Modeling of solid-liquid flow inside conical diverging sections using computational fluid dynamics approach

CFD approach to modelling, hydrodynamic analysis and motion characteristics of a laboratory underwater glider with experimental results

In the present study, the computational fluid dynamics (CFD) method was utilized to explore the rheological behavior of the flat solar collector. ANSYS 16.1 has been used to do an analysis on the drafted three-dimensional model. In order to investigate the heat transmission from the solar panel to the fluid, a CFD tool has been used. The effectiveness of the heat transfer across the entire system has been evaluated with the help of Nano fluid. Both 0.3 and 0.5 meters per second might be considered the speed of the water. These results have been compared to others and validated in accordance with those standards. The most recent findings from this line of investigation have shown that include a greater number of specifics in the working fluid of the system can contribute to an increase in the temperature at which the solar plate discharges its heat. In addition to this, it is possible to get the highest possible temperature by bringing the velocity value down to its lowest possible range.

Three-dimensional simulations of peripheral, deep venous flow during muscular exercise in limbs of healthy subjects and in those with venous dysfunction were carried out by a computational fluid-dynamics (CFD) approach using the STAR CCM + platform. The aim was to assess the effects of valvular incompetence on the venous calf pump efficiency. The model idealizes the lower limb circulation by a single artery, a capillary bed represented by a porous region and a single vein. The focus is on a segment of the circuit which mimics a typical deep vein at the level of the calf muscle, such as the right posterior tibial vein. Valves are idealized as ball valves, and periodic muscle contractions are given by imposing time-dependent boundary conditions to the calf segment wall. Flow measurements were performed in two cross-sections downstream and upstream of the calf pump. Model results demonstrate a reduced venous return for incompetent valves during calf exercise. Two different degrees of valvular incompetence are considered, by restricting the motion of one or both valves. Model results showed that only the proximal valve is critical, with a 30% reduction of venous return during calf exercise in case of valvular incompetence: the net flow volume ejected by the calf in central direction was 0.14 mL per working cycle, against 0.2 mL for simulated healthy limbs. This finding appeared to be consistent with a 25% reduction of the calf ejection fraction, experimentally observed in chronic venous disease limbs compared with healthy limbs.

The static and dynamic derivatives have been investigated for a representative UCAV by a Computational Fluid Dynamic (CFD) approach based on the capability of elsA software. The configuration, named SACCON for Stability And Control CONfiguration, is a blended wing body with a moderately swept angle which has been developed for the purpose of this project. This CFD approach is based on static computations to determine the static derivatives and on the ALE (Arbitrary Lagrangian Euler) method coupled to steady or unsteady computations to obtain the dynamic derivatives. The computed and experimental global coefficients are compared as well as sectional pressure coefficients measured in DNWNWB wind-tunnel. The effects of sting support have been evaluated: the prediction of lift is improved with respect with the experimental data. The unsteady CFD results reproduce the complex dynamic behavior including for off design condition with non linear aerodynamic effects. The effect of the transition has been computed and compared to experimental results at low incidence.

The aerodynamic performance of a three-wheeled vehicle was analysed using a Computational Fluid Dynamics (CFD) approach to evaluate its drag coefficient (Cd) and lift coefficient (Cl) under varying flow and environmental conditions. The study investigates the effects of velocity, air temperature, and density on aerodynamic forces, providing insights into their influence on vehicle stability and efficiency. A parametric analysis was conducted over a range of velocities (1–100 m/s), temperatures (223–328 K), and air densities corresponding to different altitudes (-1000 m to 80,000 m). The results indicate a direct correlation between velocity and aerodynamic forces, with Cd and Cl increasing non-linearly at higher speeds. Conversely, temperature variations showed negligible impact on aerodynamic performance, while decreasing air density at higher altitudes significantly reduced drag and lift forces. Additionally, a grid independence test was performed to ensure numerical accuracy, confirming that mesh refinement beyond a critical threshold yielded minimal variation in results. The three-dimensional model of the vehicle was developed in Fusion 360, and CFD simulations were conducted using ANSYS to assess aerodynamic behavior. The findings highlight the potential for aerodynamic optimization in three-wheeled vehicle design, emphasizing the need for refined body shaping and flow management strategies to enhance efficiency and stability. The motivation behind selecting a three-wheeled vehicle lies in its growing adoption for urban mobility, given its lightweight structure, lower manufacturing costs, and energy efficiency. However, its aerodynamic characteristics remain a critical factor in ensuring stability, particularly at higher speeds. This study highlights the potential for aerodynamic optimization in three-wheeled vehicle design, emphasizing the need for refined body shaping and flow management strategies to enhance efficiency and stability. This study serves as a foundation for future aerodynamic improvements in alternative vehicle designs, contributing to advancements in energy-efficient transportation.

This study describes a methodology combining a recently proposed renormalization inversion technique with a building‐resolving computational fluid dynamics (CFD) approach for source retrieval in the geometrically complex urban regions. It presents the first application of the renormalization inversion approach to estimate an unknown continuous point release in real situations at an urban scale. The renormalization inversion approach is based on an adjoint source‐receptor relationship and is purely deterministic in nature. The source parameters (i.e., source location and release rate) are reconstructed from a finite set of point measurements of concentration acquired from some sensors and the adjoint functions computed from a CFD model fluidyn‐PANACHE that is able to represent the geometric and flow complexity inherent in the urban regions. The inversion procedure is evaluated for a point source reconstruction using measurements from the Mock Urban Setting Test (MUST) field experiment. Source reconstructions are performed for 20 trials of the MUST experiment of a continuous point release in an idealized urban geometry consisting of a regular array of shipping containers. The steady state flow fields are computed by solving the three‐dimensional Reynolds‐averaged Navier‐Stokes equations by using a finite volume scheme. Then, in each MUST trial adjoint functions are obtained and used for the source identification. Inversion results are presented with both synthetic and real measurements in various atmospheric stabilities varying from neutral to stable and very stable conditions. With real concentration measurements, the point source is retrieved within an average Euclidean distance of 14.6 m from the actual source location. The estimated source intensity is overpredicted by an average factor of 1.37 of the true release rate. In a posterior uncertainty analysis with 10% random noise in measurements, it is demonstrated that standard deviation in the location error and release strength, respectively, varies by 5.22 m and ∼21% from their mean value for all 20 trials. A sensitivity analysis shows that the use of nonzero measurements helps in reducing the uncertainties involved in the source reconstruction. The source reconstruction results in various stability conditions exhibit the reliability of the renormalization inversion methodology coupled with the CFD approach in an urban area. The present methodology can be used by emergency regulators as a tool to detect the unknown accidental or deliberated releases in the complex urban environments.

Cementing restorations to implants is a widely used clinical procedure. Little is known about the dynamics of this process. Using a systems approach and advanced computing software modeling this can be investigated virtually. These models require validation against real-life models. The study aims to consider the system effect of a crown, abutment, and cement flow under different conditions and comparing real physical models to virtual computer simulations. A physical model of implant abutments and crowns provided three groups according to abutment screw access modification (n = 9): open (OA), closed (CA), and internal vented (IVA) abutment groups. Crowns were cemented using standardized amounts and site application. Proportion of cement retained within the crown-abutment system was recorded and compared. Differences among groups were identified using analysis of variance (ANOVA) with Tukey's post hoc test (α ≤ 0.05). Three-dimensional multiphysics numerical stimulation software (STAR-CCM+, CD-adapco) with computational fluid dynamics (CFD) approach was applied to a virtual model system of a scanned abutment and crown system. Three-dimensional real-time model simulations of cement and air displacement were produced, evaluating cement application site, speed of crown seating, and abutment modifications. Statistically significant differences in cement retained within the system (p < 0.01) were found among the IVA > OA > OCA abutment groups. The CFD virtual simulations followed this trend. Site application and speed of seating also affected cement extrusion and cement marginal infill. Fast crown seating and occlusal cement site application produced air incorporation at the margins. The CFD approach provides a convenient way to evaluate crown-cement-implant abutment systems with respect to cement flow. Preliminary evaluation indicates that the results achieved follow those of a physical actual cement-retained crown-implant abutment study.

Flow modelling and energy consumption of a hydrotransportation system possessing variable flow boundaries

The performance of the turning diffuser regardless of its expansion type, i.e., two-dimensional (2-D) or three-dimensional (3-D), has been traditionally rated using the guidelines established specifically for a 2-D turning diffuser. This has provided merely an approximation and has often led to an inaccurate prediction of 3-D turning diffuser performance. On top of that, the existing guidelines have just integrated the geometrical effect by discounting the effect of operating condition on the turning diffuser performance. Therefore, the current work aims to experimentally and numerically investigate the performance of 2-D and 3-D turning diffusers for various geometrical and operating parameters. The performance indexes (pressure recovery coefficient, flow uniformity index) as a function of geometrical (inner wall length to inlet throat width ratio, outlet-inlet configurations) and operating (inflow Reynolds number) parameters are correlated by means of Asymptotic Computational Fluid Dynamics technique. Stereoscopic particle image velocimetry was used to examine the flow characteristics, and a manometer provided the inlet and outlet wall static pressures. Among all the models tried, the best results were obtained with the standard k- and enhanced wall treatment of y+  1.1 – 1.8 was applied for the intensive simulation. Results showed that there was a potential performance of applying 3-D turning diffuser relative to 2-D turning diffuser. The 3-D turning diffuser provided higher pressure recovery at low inflow Reynolds number, Rein = 5.786 x 104 - 6.382 x 104 and better flow uniformity at high inflow Reynolds number, Rein = 1.027 x 105 – 1.775 x 105 than the 2-D turning diffuser. Minimal flow separation occured within the 3-D turning diffuser that was close to the outlet edge, 0.9Lin/W1. While flow separation within the 2-D turning diffuser took place earlier on half of the inner wall length, 0.5Lin/W1. Secondary flow vortices initially emerged at Rein = 1.027 x 105 (3-D turning diffuser) and Rein = 1.397 x 105 (2-D turning diffuser). The pressure recovery was affected mainly by the existence of flow separation and vortices, whereas the flow uniformity was affected by the dispersion of core and secondary flows. A high free-stream turbulent intensity imposed on the flow favoured the overall performance of the turning diffuser by suppressing the separation of the inner wall boundary layer and mixing to give better uniformity of the flow. Excessive elongations, Lin/W1 ≥ 20 (2-D turning diffuser) and Lin/W1 ≥ 9 (3-D turning diffuser) inherently impaired the pressure recovery. The performance correlations as a function of geometrical and operating parameters for 2-D and 3-D turning diffusers were successfully developed to satisfy both the CFD and experimental results within ±8%. In conclusion, the physics of flow particularly within the 3-D turning diffuser have been grasped with credible performance data have been established as benchmark. The developed correlations can be used henceforth by one to evaluate the performance of turning diffusers without necessarily running the full simulation or experiment. For future work, the same outlined methods particularly via Asymptotic Computational Fluid Dynamics can be applied to develop performance correlations of other diffuser types. The current work can be further extended by considering the variation of turning angles and installation of flow control devices to improve the performance of turning diffusers. The effects of skin friction and turbulent intensity should be also looked into more details.

Simulation of tidal turbine array using coupled Computational Fluid and Rigid Body Dynamics

The aerodynamic losses in centrifugal compressors are mainly associated with the separated flow on the suction sides of impeller and diffuser vanes. The overall performance of such compressors can be improved by adding splitter vanes. The present work examines the effect of varying the geometrical location of the splitter vanes in the diffuser on the overall performance of a high-speed centrifugal compressor stage of a small gas turbine. To increase the pressure recovery through the diffuser, two radial sets of vanes are used. The first set of vanes (diffuser-1) is equipped with splitter vanes, placed mid-distance between the main vanes, while the vanes of the second set (diffuser-2) are conventional vanes. Flow through the compressor was simulated using the ANSYS 19 workbench program. Flow characteristics and compressor performance were obtained and analyzed for different circumferential positions of the splitting vanes relative to the main vanes of diffuser-1. The study covered seven positions of the splitter vanes including the original design of the diffuser where the splitter vanes were located at mid-distance between the main vanes. The analysis shows that, at design conditions, selecting the position of the splitter vanes to be nearer to the pressure side of the main vanes improves the stage performance. In the present study, locating the splitters at 33% of the angular distance between the main vanes leads to the best performance, and a significant improvement in the overall stage performance is recorded. The pressure recovery coefficient is raised by about 17%, the pressure ratio is increased by about 1.13%, and the stage efficiency is increased by about 2.01%, compared to the original splitter position. Performance improvement is related to the suppression of the flow separation and the more uniformity of flow. On the contrary, further moving the splitter closer to the main blade, the pressure recovery coefficient is decreased by about 2% than the position of 33% of the angular distance, but still higher than the original position by about 15% and a limited improvement in the compressor performance is noticed. Moving the splitter far out the main blade annihilates the static pressure recovery of the diffuser by about 2:7% compared with the original position. So, for the investigated compressor, the best position of the splitter blade in the circumferential direction, which provides the best stage performance in our parametric analysis, is not necessary to be at the mid-angular distance between the diffuser’s main blades, but it is achieved by moving the splitter to about 33% of the angular distance where the diminished loss from the suppressed flow separation is more prevailing and the instigated friction losses from splitter surfaces are less critical.

The size distribution of silica particles as a model material from colloidal silica solution precursor in the flame assisted spray dryer method were studied numerically using Computational Fluid Dynamics (CFD). CFD has ability to solve the momentum, energy and mass transfer equation well. k-ε model was used to describe the turbulence model and non-premixed combustion model was used to combustion model. Collision and break-up model were also considered to predict the final particles size distribution. For validation, LPG with flow rate of 0.5 L/minute LPG and 200% excess air were used as energy sources. At this condition, numerical solution agreed well to the experimental work resulting in polydisperse size distribution. Therefore, others excess air, 100% and 150% were also observed using CFD and evaluated their contribution to their particles size distribution. Monodisperse particles size distribution were obtained when the combustion used 150% excess air.

Heat treatment of metal is an energy intensive process. Currently direct electrical energy is employed for this purpose. The harnessed heat using concentrated solar thermal technology can be employed for processing of metal, like, annealing of Aluminium. This paper presents a technology that uses solar energy as fuel and converts the harnessed heat for this purpose. An existing heat treatment furnace is scaled down and retrofitted to demonstrate solar convective heating concept. Air-flow velocity measurements in furnace side-duct are performed using laser Doppler velocimeter (LDV) along the centerline of injection circular nozzle. Comparison with the reported impinging jet profiles shows that air-flow in the side-duct is asymmetric. Computational fluid dynamics (CFD) approach based on different turbulent models is used for air-flow analysis. The selected CFD approach is validated by comparing measured velocities. Validated CFD tool is used for details flow analysis in the furnace. Detailed analysis revealed the formation of a vortex structure under the heart region, which is expected to influence the metal processing quality.

This paper presents a comparison study of the aerodynamic behavior of an 8 MW wind turbine operating under yawed conditions using field measurements, Blade Element Momentum (BEM) theory and Computational Fluid Dynamics (CFD). Turbulent inflow wind field measurements are used to generate an IEC-compliant turbulence box upstream of the wind turbine that is used within the BEM tool MoWiT and the CFD tool chain by IWES in OpenFOAM. Both simulation approaches take into account blade flexibility using modal reduced, anisotropic beam elements in BEM and Geometrically Exact Beam Therory (GEBT) in CFD. While the focus is being set towards the CFD approach, turbine power output, blade root bending moments and blade tip deflections are analyzed. It is shown that both modeling approaches react differently towards the generated wind field.

In this paper, single pass fin type solar air heater has been optimised to get better thermal performance using computational fluid dynamics (CFD) technique (Fluent 6.3 and Gambit 2.3). Four important parameters namely mass flow rate, number of fins, fin height and length have been considered. DTRM and RNG k-ε turbulence model were used and the simulation results have been validated with the results of experimental study performed during March, 2012. During the CFD analysis outlet air temperature, air temperature rise, heat gain by the air and instantaneous efficiency has been determined. Simulation results suggest that the SAH should have four fins, i.e., same as in existing SAH but fin length and height should increase from 40 cm to 50 cm and 4 cm to 6 cm respectively for superior performance. In optimised SAH, instantaneous efficiency and useful heat gain improved by 8.35% and 8.24% respectively with air mass flow rate of 0.024 kg/s as compared to SAH.