Speeding-Up Physical Systems Modeling with Object-Oriented Programming

<div class="htmlview paragraph">The design objective of the Spicer S400-S axle program was to develop a light weight, lower torsional vibration, long life tandem drive axle for the heavy truck industry. This was accomplished with the incorporation of a number of new product features and technical advancements, both in design and manufacturing. These include:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"> <div class="htmlview paragraph">reduced standouts for improved interaxle driveline angles</div> </li> <li class="list-item"> <div class="htmlview paragraph">use of finite element analysis</div> </li> <li class="list-item"> <div class="htmlview paragraph">fixed pinion mounting</div> </li> <li class="list-item"> <div class="htmlview paragraph">optimization of lube flow and direction of lubrication</div> </li> <li class="list-item"> <div class="htmlview paragraph">optimized gear design for improved strength and noise reduction.</div> </li> </ul> </div> <div class="htmlview paragraph">This paper focuses on these features and also on the development process for the axle, including the use of simultaneous engineering. Utilizing simultaneous engineering, the S400-S was developed from concept to full production in fifteen months.</div>

<div class="htmlview paragraph">One of the best ways to improve the quality and reduce the cost of software is to increase software reuse. One of the best technologies for increasing software reuse is object-oriented programming. Languages like C++ are making object-oriented programming accessible to more people, but many do not realize the impact that increasing reuse can have on the software development process. Reusable software is easy to use, but hard to produce. Object-oriented programming decreases the time spent coding and debugging, but increases the proportion of time spent designing. Object-oriented programming can have a big pay-off, but like all new technologies it has costs and risks, and the most successful uses of object-oriented programming are by those who are aware of the potential problems.</div>

<div class="htmlview paragraph">Increasingly, manufacturers are looking to computer simulation methods to accurately assess ride quality potential of new vehicle designs as they are being developed. This requires detailed multi-body dynamic models to be developed with sufficient fidelity to replicate ride relevant phenomenon. These models must have the capability to:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">Represent the distributed mass and elasticity of the vehicle structures (e.g. frame ladder, cab, and trailer).</div></li> <li class="list-item"><div class="htmlview paragraph">Include the non-linear behavior of shock absorbers and elastomeric components.</div></li> <li class="list-item"><div class="htmlview paragraph">Reproduce the fundamental system dynamics that influence ride.</div></li> <li class="list-item"><div class="htmlview paragraph">Provide output of the acceleration, velocity, and displacement measures needed to compute ride quality.</div></li> </ul> </div> <div class="htmlview paragraph">This paper discusses the development of an ADAMS multi-body dynamic model of a tractor semi-trailer for use as a predictive tool in evaluating ride quality design improvements. The model includes flexible representations of the frame, cab, and trailer generated from finite element models through the use of component mode synthesis. Non-linearities and viscoelastic effects associated with compliant elements and dampers are selectively incorporated using explicit functions and spline/surface interpolation. Road inputs into the suspension are generated via tire elements in contact with road profiles or by prescribing axle motions. Additionally, a ride quality algorithm is built into the model allowing virtual ride measurements to be taken and compared to physical test results.</div> <div class="htmlview paragraph">Construction and correlation of the model followed a multi-step process in which each of the major subsystems were built and validated to test results prior to incorporation in the full vehicle model. Ride data from a vehicle instrumented with 70 transducers was collected on highway routes and used to support full vehicle correlation.</div> <div class="htmlview paragraph">The ability of the model to predict ride quality variations due to changes in vehicle configuration was tested by evaluating several case studies. These results are presented along with details of the model construction and correlation process.</div>

<div class="htmlview paragraph">Engine manufacturers and product designers are currently under significant pressure to reduce fuel consumption, emissions, and noise from two-stroke engines. Improved engine breathing goes a long way toward overcoming these challenges by providing better charge delivery, complete exhaust gas scavenging, and minimal fuel short-circuiting.</div> <div class="htmlview paragraph">Reed valve motion and the resulting gas flow are highly coupled phenomena. Understanding and controlling these dynamics and their interactions is critical to effective intake breathing. A comprehensive effort to model reed valves at a level sufficient for engine design using engine simulations is still incomplete. This work is focused on the assessment, development and validation of a reed valve model suitable for engine simulations.</div> <div class="htmlview paragraph">In this work, a representative two-stroke engine reed valve is modeled in a detailed fluid/structures, multi-physics CFD code which fully resolves both the flow-field and the details of the deflecting reed plate.</div> <div class="htmlview paragraph">This same reed valve geometry is modeled in a 1D engine simulations code. In lieu of detailed experimental measurements, the CFD simulation results are used to provide the flow and lift data for various differential pressures. These are input into the 1D model as flow coefficients vs. lift.</div> <div class="htmlview paragraph">A comparison of results, between the 1D engine simulation and the original fluid/structure CFD, shows excellent agreement for the maximum lift, the lift vs. time profile, and for the overall flow predictions.</div> <div class="htmlview paragraph">In the 1D simulation code, the standard component model representation of a reed valve is as a spring-mass-damper physical model. It was found that this model, while not an exact representation of the bending reed, did provide adequate agreement.</div> <div class="htmlview paragraph">Additionally, the predicted lifts were compared with uniformly loaded deflecting beam theory assuming the up-stream and down-steam pressures are uniformly applied on either side of the reed valve. It was found that the while this assumption is an adequate first level approximation for low lift conditions and suitable for preliminary design analysis, the CFD results indicate that it does not hold for high lift conditions.</div> <div class="htmlview paragraph">In this work, a method was demonstrated which allows design engineers to investigate reed valve design options from the detailed CFD perspective and from the 1D engine simulations perspective, and thus to develop a good reed valve model for analysis prior to testing. This allows the engineer to screen potential designs with simulation before the more expensive task of building and testing prototypes. The validated reed valve model can be incorporated directly into a full engine simulation with confidence.</div>

<div class="htmlview paragraph">“As we handle more operations and passengers in the air, we must make certain we have the capacity to handle increased traffic on the ground.”</div> <div class="htmlview paragraph">- Jane Garvey, FAA Administrator (4/20/98)</div> <div class="htmlview paragraph">The FAA Technical Center (Aviation System Analysis and Modeling Branch, ACT-520) has been responsive to the FAA Airport Capacity Program customers for the past 22 years, developing, testing, and applying airfield and airspace simulation models. More than 90 capacity studies have been completed with ACT-520 personnel contributing their technical expertise to the Airport Design Teams. The teams are comprised of FAA personnel, airport operators, air carriers, other airport users and aviation industry representatives at major airports throughout the US.</div> <div class="htmlview paragraph">Initial studies focused on modeling airport operations from final approach, taxi, gate operations and departure processing. Later in the program, local airspace studies were included in some airport study efforts. Both airport and airspace studies include either a full scale design team study or a less detailed tactical initiative. Recently, National Airspace System (NAS) modeling personnel joined the group providing system modeling expertise in the NAS Architecture and Flight 2000 programs.</div> <div class="htmlview paragraph">An arsenal of analysis tools and computer simulation programs has been developed and tested to accomplish each task. The group has experience using the models they have developed or improved upon (ADSIM, RDSIM, RQSIM, etc.), have obtained from other FAA entities (SIMMOD, NASPAC, RAAM, etc.) and have acquired under contract or agreements (The Airport Machine, TAAM, MIT Delays Model, etc.). This modeling capability permitted the group to perform simulations of improvements in the categories of airfield, facilities and equipment, ATC operational, and airport policy improvements. The delay effects of aircraft demand (schedules), fleet mix, runway configurations, weather, aircraft separation standards, etc., were measured in the studies.</div> <div class="htmlview paragraph">Future studies will require new model development particularly in the arena of system wide impacts measured on an annual basis. The requirement for an analyst to know both the model inputs and the working of the model's code will continue to apply for a successful study. As in the past, no universal model will answer every question and existing models will require enhancements to reflect unique requirements. Because of the increases in computing speed and memory, the fidelity of simulations can be enhanced in the near future through new hardware acquisitions.</div> <div class="htmlview paragraph">ACT 520's past participation in this enterprise has generated an understanding of the interrelationships of various airport and airline systems. Our seven senior analysts and eight junior analysts combined with their professional expertise are ready to address the FAA Administrator's concerns about capacity.</div>

<div class="section abstract"><div class="htmlview paragraph">In recent years the 2-wheelers engines companies have been focused on increasing the overall engine efficiency, that can be achieved amongst other by engine down-speeding, engine down-sizing and by reducing the frictions; however, to maintain or improve vehicle performance, it is necessary to provide a corresponding increase in specific power.</div><div class="htmlview paragraph">In accordance with these trends, the studied approaches and methodologies have been exploited, during the development of the new Piaggio small scooter engine.</div><div class="htmlview paragraph">In this work a multi-objective analysis has been applied to the valve train system design, in order to optimize the engine performance in terms of friction reduction, power curve and timing system response. Along with this optimization methodology, a robust design has been studied to make the peak cranking compression pressure insensitive to the engine starting device working. These calculation methodologies have been followed using commercial software as GT-SUITE® code and the modeFRONTIER® platform for the multi-objective optimization analysis.</div><div class="htmlview paragraph">The several configurations investigated have allowed to reach the desired trade-off between the appropriate and efficient valve train behavior and the engine performances.</div><div class="htmlview paragraph">The global engine friction reduction has been obtained thanks to low resisting cam torque profiles, a specific valve springs set and a new compression releaser device (during engine starting phase).</div><div class="htmlview paragraph">The results have been further validated by an experimental campaign carried out on the test bench for engine performance and on the specific cold test bench to evaluate friction losses.</div></div>

<div class="htmlview paragraph">In the past decade, SCR deNOx technology with urea injection has grown to maturity. European OEMs will apply SCR deNOx to meet future heavy-duty emissions legislation starting with EURO-4 (2005/2006). Numerous research programs in Europe and the US have shown a variety of system layouts and control strategies. The main differences are formed by:</div> <div class="htmlview paragraph"> <ul class="list disc"> <li class="list-item"><div class="htmlview paragraph">the engine-out NO<sub>x</sub> calibration</div> </li> <li class="list-item"><div class="htmlview paragraph">the application of an NO to NO<sub>2</sub> catalyst</div> </li> <li class="list-item"><div class="htmlview paragraph">open-loop or closed-loop urea dosage control.</div> </li> </ul> </div> <div class="htmlview paragraph">This paper gives an overview of possible SCR system configurations that are required for different stages of future emission legislation.</div> <div class="htmlview paragraph">Engine-out NO<sub>x</sub> emission is strongly influenced by ambient conditions. Projections in this study show that a combination of cold climate and a wintergrade fuel is the most severe: it may lead to 30% lower engine-out NO<sub>x</sub> emission with respect to laboratory conditions. The varying engine-out NO<sub>x</sub> emission requires a safety margin in the case of an open-loop controlled system in order to avoid excessive NH<sub>3</sub> slip.</div> <div class="htmlview paragraph">Calculations in this paper show that Euro 4 limits can be met with open-loop controlled urea dosage; an NO to NO<sub>2</sub> catalyst is even not required. For other future emission legislation (Euro 5, US 2007 and US 2010), it becomes difficult to safely achieve the limits with open-loop control. US 2007 and 2010 legislation require an NO to NO<sub>2</sub> catalyst because of the low average load and consequently low exhaust gas temperatures. Engines that are developed to meet US 2010 legislation need special measures to increase the exhaust gas temperature and to reduce engine-out NO<sub>x</sub> below 2 g/kWh.</div> <div class="htmlview paragraph">In all cases, optimal hydrolysis and mixing conditions are of major importance. High speed photography and droplet size measurements are presented as methods for characterizing and modeling aqueous urea spray patterns. The information from these measurements is used as input parameters for simulation tools. These consist of a 2D/3D CFD program for urea mixing analysis and a 1D SCR system model for development of dosage control and optimization of catalyst dimension.</div> <div class="htmlview paragraph">Finally, simulations with the SCR system model are compared with measurements on the engine test bench.</div>

<div class="">In this work, we demonstrate the importance of High Performance Computing (HPC) and Urgent Computing (UC) in rapid disaster response to man-made catastrophes. Using the specific case study of a potential dam breach at the Kyiv cistern reservoir in Ukraine, we show how these technologies can be used to assess the potential hazards and impacts of such an event.</div> <div class=""> </div> <div class="">The Copernicus Emergency Management Service Risk & Recovery Mapping service was activated to derive hazard assessment mapping for the protection of citizens and infrastructure in the event of a potential dam breach. The Kiev Hydroelectric Power Plant, located upstream of Kiev, has been the target of a previous rocket attack, and the threat of another successful attack cannot be ruled out. <span class="">The potential consequences of a dam breach are severe and include flooding and the erosion and transport of radioactive sediment.</span><span class=""> </span></div> <div class=""> </div> <div class="">To determine the impact of a potential dam breach and predict its effects on citizens and infrastructure, we used the Dambreak-HySEA model, which is part of the HySEA suite. This model is specifically designed to accurately reproduce the evolution of wet/dry fronts in geophysical flows such as river flooding, flooding in rural and urban areas, and dam failures. Developed by the research group EDANYA of the University of Malaga, the model was implemented using Graphics Processor Units (GPUs) with CUDA, resulting in a significant speed-up compared to a traditional CPU implementation.</div> <div class=""> </div> <div class="">The use of HPC resources, specifically those provided by the Spanish Network for Supercomputing (RES) program Urgent computing for citizen problems, was crucial in obtaining the results within the 10-day delivery time frame with the simulation of four scenarios required by the activation: partial and complete breakage of the Kyiv Dam and the same scenarios for the Irpin Dam. These simulations were computationally complex, requiring the solution of nearly 700 million computational cells per scenario.</div> <div class=""> </div> <div class="">Overall, this study highlights the importance of utilizing HPC and UC in disaster response and risk management. By utilizing advanced numerical models and computational resources, we can more accurately predict the potential hazards and impacts of man-made catastrophes such as dam breaches, and take necessary measures to protect citizens and infrastructure.</div>

<div class="htmlview paragraph">The purpose of this paper is to provide a comprehensive review of the laws, implementing regulations, and industry consensus standards that form the basis for the design, manufacturing, and use of commercial vehicles (CVs) and their operation in highway and off-road settings.</div> <div class="htmlview paragraph">The paper begins with an introduction to CVs as transporters of people and goods and as enablers for the provision of services. It briefly describes governmental interest in CV safety and the use of CVs as tools in systems - including the importance of safety research and technology assessment programs. The safety focus is described in terms of the Haddon Matrix, a safety model that shows the time and activity relationships between the operator, vehicle, and environment.</div> <div class="htmlview paragraph">Next, the paper provides a history of important safety legislation related to vehicle design, manufacture, and operation. Although the primary focus is on highway CVs (generally referred to as commercial motor vehicles, or CMVs) in the United States, the paper also briefly addresses laws relating to the safety of off-road agricultural vehicles, and construction and mining vehicles. The paper also touches on laws and regulations applicable to these vehicles and their operation in place in Canada, the European Union, Australia, and other nations.</div> <div class="htmlview paragraph">Many government agencies and non-governmental organizations have CV safety responsibilities - including issuing regulations (consensus standards in the case of the non-governmental organizations) and assuring compliance through various oversight mechanisms. The paper describes their various roles and responsibilities focusing particularly on North America and Europe. This is followed by a discussion of how regulations are developed and implemented.</div> <div class="htmlview paragraph">A series of case studies is used to illustrate the application legal, regulatory, and standards development processes to specific CV safety challenges. The case studies discuss highway CV weights and dimensions, brakes, rear impact protection devices, retroreflective marking, speed limiting devices and onboard data recorders, and rollover protection devices for off-highway vehicles.</div> <div class="htmlview paragraph">The paper closes with a discussion of the continuing need to ensure CV safety through cooperative research and technology assessment activities, as well as the need for designers and engineers to maintain an awareness of the changing environments that influence CVs' use.</div>

<div class="section abstract"><div class="htmlview paragraph">A follow-up case study on rollover testing with a single full-size sport utility vehicle (SUV) was conducted under controlled real-world conditions. The purpose of this study was to conduct a well-documented rollover event that could be utilized in evaluating various methods and techniques over the phases associated with rollover accidents. The phases documented and discussed, inherent to rollovers, are: pre-trip, trip, and rolling phases.</div><div class="htmlview paragraph">With recent advances in technology, new devices and techniques have been designed which improve the ability to capture and document the unpredictable dynamic events surrounding vehicle rollovers. One such device is an inertial measurement unit (IMU), which utilizes GPS technology along with integrated sensors to report and record measured dynamic parameters real-time. The data obtained from a RT-4003 IMU device are presented and compared along with previous test data and methodology.</div><div class="htmlview paragraph">For this case study, an instrumented 1996 GMC Jimmy SUV was towed to 53.6 mph (86.3 kph) and released. An automated pre-programmed controller steered the vehicle through maneuvers intended to result in rollover. The SUV rolled 2 revolutions and was documented with both on and off-board instrumentation, videotape footage, survey measurements, and numerous high-resolution three-dimensional (3D) laser scans. The data were then compared and contrasted with previously published rollover techniques and methodologies.</div><div class="htmlview paragraph">This instrumented case study is a well-documented test that can be utilized in accident reconstruction for future evaluation, comparison, or simulation of similar type rollover events.</div></div>

<div class="htmlview paragraph">The case study approach, as an educational tool, has achieved widespread use in a variety of disciplines. The case method affords several advantages over conventional and traditional lecture methods of education, but the degree of effectiveness of the case study approach varies considerably between different disciplines. Therefore, an interdisciplinary comparison of case study techniques may be of some value in improving the case study methods used in engineering studies.</div> <div class="htmlview paragraph">The most notable applications of case methods include the areas of business and management decision making, medicine, the social sciences, and engineering. The Harvard School of Business has established the pattern for business case studies. Much of today's accepted medical practice is based on “case studies.” Many significant sociological and psychological findings are based on case studies, while engineering case studies can be applied to achieve a wide variety of objectives including creativity in design, technical feasibility, etc. The analysis of the case study historically applied in each discipline reveals certain characteristics which seem to be unique to each area of case study application. Interdisciplinary comparison also reveals basic differences in case study techniques. Some of these differences lie in the nature of the discipline itself, while some are based upon extraneous causes which are completely unrelated to the area of study.</div> <div class="htmlview paragraph">On the basis of the interdisciplinary analysis and comparison, certain conclusions may be drawn regarding the effectiveness of the engineering case study. The evidence seems to indicate that there is far more potential for improvement in the engineering case study than in the other areas considered. The basic recommendation resulting from the comparison of case study methods is that engineering educators incorporate more case studies into their courses. Engineering educators should also integrate into their case studies as many as possible of the characteristics of successfully proven case study techniques used in other disciplines.</div>

<div class="section abstract"><div class="htmlview paragraph">In recent years, diesel engine emissions regulations have been strengthened worldwide, necessitating the evaluation of regulatory values under transient conditions. Consequently, the need to assess transient states in the development of diesel engines has increased significantly. The evaluation using MBD (Model Based Development) is considered a promising method for achieving both low fuel consumption and simultaneous reduction of NOx and soot emissions. However, the mechanism of soot formation is complex, making it challenging to model mathematically directly. In this paper, hybrid machine learning approaches combining a physical model and a machine learning model are used to validate the prediction of soot emissions under transient conditions in a diesel engine with an EGR system. Various parameters such as fuel consumption and emissions predicted by the physical model are compared with measurements to validate the accuracy of the physical model. The prediction of soot emissions by the physical model is based on the Hiroyasu model. From these results, it is demonstrated that the physical model has sufficient accuracy to be used in hybrid machine learning approaches. However, it is shown that the physical model is inadequate as a prediction approach for soot emissions. Gaussian Process Regression (GPR), Support Vector Regression (SVR), Random Forest (RF), and Gradient Boosting Decision Tree (GBDT) are used to develop the machine learning models, and each model is trained on data under steady-state conditions. The prediction accuracy of each model and the physical model is compared and validated. The results show that the hybrid machine learning approaches have higher predictive accuracy than the physical model for soot emissions predictions in both steady-state and transient conditions. The GPR model with the highest prediction accuracy shows a test R<sup>2</sup> of 0.87 under steady-state conditions and relative errors with the measured values of less than 10% for both Non-load Transient Cycle (NRTC) and Low Load Cycle (LLC), which are engine test cycles.</div></div>

<div class="section abstract"><div class="htmlview paragraph">A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall. Many physical phenomena are associated with the operation of the system piston-ring-cylinder (PRC), such as: inter-ring gas dynamics for the labyrinth seal, hydrodynamic lubrication and mixed friction in gaps between the rings and cylinder liner, oil flow and distribution of lubricant along the liner, twist motion of rings, liner temperature influence on the oil viscosity.</div><div class="htmlview paragraph">The first part of the paper presents a comprehensive model of the PRC system developed by the author. Among own models it includes several models taken from literature, like: a model of viscous oil flow between rough gap surfaces formulated by Patir & Cheng and an elastic contact model of Greenwood & Tripp.</div><div class="htmlview paragraph">The main parts of developed mathematical model and software have been experimentally verified during a research period of the author at the marine engine designing centre ”Wärtsilä” in Switzerland. A relatively good qualitative and quantitative compatibility between the experimental measurements and calculated results has been achieved.</div><div class="htmlview paragraph">In contrast to the previous papers of the author concerning the piston ring pack operation of IC engines, a part of new calculation results for an automotive internal combustion engine have been presented. These results include basic physical quantities associated with gas and oil flow processes in the PRC system for the analyzed engine.</div><div class="htmlview paragraph">The developed simulation model can be utilized for: evaluation of gas leakage through the sealing ring set, prediction of lubrication conditions of piston rings and oil consumption, defining areas of the possible cylinder liner wear and profile changes of piston rings sliding surfaces, and thus can be useful for optimization of the PRC system design.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Today, most vehicles in developing countries are equipped with air conditioning systems that work with Hydro-Fluoro-Carbons (HFC) based refrigerants. These refrigerants are potential greenhouse gases with a high global warming potential (GWP) that adversely impact the environment. Without the rapid phasedown of HFCs under the Kigali Amendment to the Montreal Protocol and other actions, Earth will soon pass climate tipping points that will be irreversible within human time dimensions. Up to half of national HFC use and emissions are for the manufacture and service of mobile air conditioning (MAC). Vehicle manufacturers supplying markets in non-Article 5 Parties have transitioned from HFC-134a (ozone-safe, GWP = 1400; TFA emissions) to Hydro-Fluoro-Olefin, HFO-1234yf (ozone-safe, GWP < 1; TFA emissions) due to comparable thermodynamic properties. However, the transition towards the phasing down of HFCs across all sectors is just beginning for Article 5 markets. Patents on R-1234yf will soon expire, just as scarcity is likely to drive the price of R-134a to historic highs.</div><div class="htmlview paragraph">This work consists of two case studies, specific to an Internal Combustion Engine (ICE) and an Electric Vehicle (EV). Two different refrigeration system architectures are examined. Both the shortlisted vehicles have different and complex AC system architectures. Complex AC system architectures are selected in this study with the objective of understanding and deploying the learnings in vehicles with less complex and simpler AC system architectures. The ICE vehicle selected for the study has a dual AC configuration with two cooling points (front and rear), using DX architecture. In the EV, an architecture similar to that of the ICE vehicle is deployed for cabin cooling, but unlike the ICE vehicle, it has a secondary coolant-based loop provisioned for battery thermal management. For this study, the baseline HFC-134a refrigerant is replaced by a ‘drop-in’ alternate low-GWP HFO-1234yf refrigerant in both vehicles.</div><div class="htmlview paragraph">This study focuses on cooling performance evaluation with existing HFC refrigerant and proposed HFO refrigerant for both AC system architectures, gap identification, and proposing common and unique solutions for bridging the performance gaps.</div></div>

<div class="htmlview paragraph">Vehicle manufacturers throughout the world are facing increasingly stringent noise legislation which demands highly refined vehicles and powertrains for compliance. Further to the demanding legislative requirements, an increase in customer awareness regarding high ride comfort has forced additional refinement as regards competitive sound level and sound quality.</div> <div class="htmlview paragraph">In the commercial vehicle market this trend in increased customer awareness is growing ever more apparent, although the expectations regarding noise are, for some applications, justifiably lower than in the passenger car market. Further to legislative compliance and a competitive noise level in dB(A), noise quality issues are increasingly being addressed to satisfy customer demand.</div> <div class="htmlview paragraph">In the passenger car market customer awareness regarding noise has increased to such an extent that in order to satisfy customer expectations engineering desirable sound has become an integral requirement.</div> <div class="htmlview paragraph">In this paper three case studies are presented based on problem focused NVH analysis. Case study 1 presents a tractor noise problem related to legislative requirements. Case study 2 is based on noise reduction of a commercial vehicle diesel engine and is integrated with a complementary section on engine structure design. The third case study is related to passenger car interior noise quality and is integrated with a section on engineering desirable sound.</div>