Complex mathematical analysis of photobioreactor system.

Background/Objectives: Optimizing drug deposition to the olfactory region is key in Nose-to-brain drug delivery strategies. However, findings from computational fluid dynamics (CFD) studies remain inconsistent concerning the parameters influencing olfactory deposition, limiting clinical translation and device optimization. This systematic review aims to identify robust CFD parameters for optimizing drug delivery to the olfactory region. Methods: A systematic review and meta-analysis were conducted following PRISMA guidelines, selecting studies reporting CFD simulations of nasal drug delivery with evaluation of olfactory deposition efficiency. The primary outcome was the correlation between each CFD parameter and olfactory deposition rate. Parameters included particle size, impaction parameter, flow rate, spray cone angle, insertion angle, injection velocity, head position, release position, and breathing pattern. Data were extracted and standardized, and statistical methods were used to assess correlations, heterogeneity, and potential biases in study results. Results: Smaller particle size (pooled r = −0.42) and lower impaction parameter (r = −0.39) were significantly associated with higher olfactory deposition. No consistent correlation was observed with breathing flow rate. Heterogeneity across studies was high (I2 > 90%). Funnel plots asymmetry suggested potential publication bias in particle-related outcomes. Conclusions: Particle characteristics, especially size and inertia, are the most critical determinants of olfactory deposition in CFD simulations. These findings support design optimization of nasal delivery devices targeting the olfactory region and underscore the need for standardized reporting and validation across CFD studies.

With the decreasing price of oil nowadays, the need to develop techniques to reduce operational costs in a field is inevitable. Formation water is a by-product obtained during oil production which is produced is produced in higher quantities than hydrocarbon. This is a major concern for oil and gas industry as separating, treating and reinjecting of the produced water into the reservoir formation requires a large amount of energy, money and time. This paper proposes a new technique for downhole separation of oil and water using a tubular centrifuge which can be integrated of the casing or the tubing string. This centrifugal downhole oil/water separator (CDOWS) will introduce the feed to a large centrifugal force which will separate both fluids based on density differences. The technology is designed for different well configurations satisfying several conditions in the industry. This paper shows and tests the model using Computational fluid dynamics (CFD) study for different designs and configurations. To validate this process in a downhole configuration, a computational fluid dynamics (CFD) study is conducted on a CAD model which was designed using a 3D modeling software. The study investigates the separation efficiency using various diameters, RPMs of the CDOWS as well as different flow rates and water cut. Furthermore, different possible designs are considered in this study. The results are then used to optimize the design of such tool in order to produce a physical model.

In order to debottleneck very large three phase production separators in a Middle Eastern oil field, new high efficiency internals were installed. A Computational Fluid Dynamics (CFD) study was conducted of these three-phase separators. The study focused on the evaluation of internal modifications and the influence of the inflow characteristics. A combination of the Eulerian-Eulerian multiphase and k-ε turbulence models was used to simulate the complex behavior of the flow inside the separator. A series of parametric case studies was conducted. The findings of the CFD study were compared with the results of field performance test. This paper describes the approach adopted in the CFD study. The geometry, mesh, numerical models, simulation strategy as well as the results and findings are discussed in detail.

Peri- or postoperative neurological complications are among the main risks for patients undergoing extracorporeal circulatory support (ECC). Two of the main reasons are an increased risk for strokes and altered flow conditions leading to cerebral hypoperfusion. This is strongly affected by cerebral autoregulation, which is the body's intrinsic ability to provide sufficient cerebral blood flow (CBF) despite changes in cerebral perfusion pressure (CPP). This complex mechanism has been mainly neglected in numerical studies, which have often been applied for analysis of ECC. In this study, a mathematical model is presented to implement cerebral autoregulation into computational fluid dynamics (CFD) studies. CFD simulations of cardiopulmonary bypass (CPB) were performed in a 3D model of the cardiovascular system, with flow variations between 4.5-6 L/min. Cerebral outlets were modeled using an equation to calculate CBF based on CPP. Assuming full regulation, CBF was kept constant for CPP between 80 and 120 mm Hg. A deviation in CBF of 20% occurred for CPP between 55-80 mm Hg and 120-145 mm Hg, respectively. The level of regulation was varied to take possible impairment of cerebral autoregulation into account. Furthermore, chronic hypertension was modeled by increasing the baseline CPP. Results indicate that even for full autoregulation, CBF is decreased during CPB. It is even lower for impaired autoregulation and hypertensive patients, demonstrating the strong impact of autoregulation on CBF. It is therefore imperative to include this mechanism into CFD studies. The presented model can help to improve CPB support conditions based on patient-specific autoregulation parameters.

Currently, the design of floating offshore wind systems is primarily based on mid-fidelity models with empirical drag forces. The tuning of the model coefficients requires data from either experiments or high-fidelity simulations. As part of the OC6 (Offshore Code Comparison Collaboration, Continued, with Correlation, and unCertainty (OC6) is a project under the International Energy Agency Wind Task 30 framework) project, the present investigation explores the latter option. A verification and validation study of computational fluid dynamics (CFD) models of the DeepCwind semisubmersible undergoing free-decay motion is performed. Several institutions provided CFD results for validation against the OC6 experimental campaign. The objective is to evaluate whether the CFD setups of the participants can provide valid estimates of the hydrodynamic damping coefficients needed by mid-fidelity models. The linear and quadratic damping coefficients and the equivalent damping ratio are chosen as metrics for validation. Large numerical uncertainties are estimated for the linear and quadratic damping coefficients; however, the equivalent damping ratios are more consistently predicted with lower uncertainty. Some difference is observed between the experimental and CFD surge-decay motion, which is caused by mechanical damping not considered in the simulations that likely originated from the mooring setup, including a Coulomb-friction-type force. Overall, the simulations and the experiment show reasonable agreement, thus demonstrating the feasibility of using CFD simulations to tune mid-fidelity models.

Experimental and CFD studies of fluid dynamic gauging in duct flows

The ventilation of multiple-bed hospital wards: Review and analysis

A systems approach for CO2 fixation from flue gas by microalgae—Theory review

Computational fluid dynamics study of phosphotungstic acid electrolyte-based fuel cell (PWAFC)

Endoscopic nasopharyngectomy represents a significant intervention for recurrent nasopharyngeal carcinoma (NPC). Various surgical techniques, including transnasal and transoral approaches, are employed. However, the impact of these procedures on nasal airflow dynamics is not well understood. This computational fluid dynamics (CFD) study aimed to investigate alterations in nasal airflow and air conditioning following endoscopic nasopharyngectomy. A 55-year-old male patient with recurrent NPC was selected, whose CT data were utilized for image reconstruction. A preoperative model and two postoperative models, including the transnasal and transoral approach models, were established. The airflow patterns and various CFD parameters were analyzed. In the postoperative models, the high-speed airflow went along the soft palate and into the nasopharyngeal outlet, and there was the low-speed turbulence in the expanded nasopharyngeal cavity. Compared to the preoperative model, the postoperative models exhibited reductions in surface-to-volume ratio, nasal resistance, airflow velocity and proportion of high wall shear stress regions in nasopharynx. The changing trends of nasopharyngeal air temperature and humidity in the preoperative and transoral models were consistent. The heating and humidification efficiency decreased in the transnasal model compared to the transoral model. The endoscopic nasopharyngectomy for recurrent NPC affects the nasal airflow and warming and humidification function. The transoral approach has less influence on aerodynamics of the upper airway compared to the transnasal approach. From a CFD perspective, the endoscopic nasopharyngectomy does not increase the risk of postoperative complications, including the empty nose syndrome and the carotid blowout syndrome.

The objective of this research is to develop models that represent the effects of light and algae and incorporate these effects within a computational fluid dynamics (CFD) model of a photobioreactor (PBR). Several factors, including nutrient availability, carbon dioxide concentration, light intensity, and frequency of high and low light intensity periods, affect the efficiency of biomass yield within a photobioreactor. However, even with a general understanding of the affecting factors, scaling up of photobioreactors from a laboratory to a commercial level exist and provide a challenge concerning efficiency. The development and execution of an integrated light, algae, and CFD model can provide insight into more cost and time efficient configurations of PBRs. In depth CFD studies have been used to predict thermal-fluid effects, including bubble-liquid interaction and temperature profiles; however, studies concerning algae-liquid interactions appear sparsely. In order to better understand up-scaling issues, new modifications of previous CFD methods incorporate an algae particle tracking method, as well as light modeling. The particle tracking method considers the individual algae cell as a volume-less and mass-less particle that follows the liquid velocity profiles within the PBR. The light model takes into account algal concentration as well as bubble location and bubble concentration. The integration of the models allows for the average intensity of light experienced by an algae cell to be numerically estimated, alongside the frequency of light and dark periods the particle experiences. The long term goal of this research is to develop an algae growth model that incorporates light intensity and the flashing light effect. The present research is a continuum of previous work aimed at pursuing the optimum design of a column PBR which is commercially viable and effective at producing algal biofuels and bioproducts.

The automotive market is continually driving the suppliers of turbochargers to push their designs into new unexplored realms. The most recent request is to have improvements to the surge margin at higher pressure ratios due to the demands of modern Diesel and gasoline engines. This study looked back at historic casing treatments and investigated the concept of axial grooves being applied to the shroud of a centrifugal compressor. This paper presents a literature review of previous centrifugal compressor casing treatments and explores in detail the axial groove type casing treatment. The study is comprised of two main sections, a test campaign and a numerical investigation. The test campaign compares the axial groove casing treatment against a baseline case without a casing treatment and a typical ported shroud casing treatment. Results are presented along with an explanation of the changes to the performance over the baseline case. The axial groove casing treatment is shown to be able to improve the surge margin as desired in a very package orientated manner. The second part of this paper looks at a similar axial groove casing treatment but for a different centrifugal compressor stage. A computational fluid dynamics (CFD) study was carried out to investigate and provide understanding to the fluid mechanics surrounding the axial groove casing treatment. The CFD and test data are not compared; rather an independent CFD study explains the basic mechanics of how the axial grooves interact with the impeller in order to explain the performance changes seen between a baseline case, and a case including the axial groove casing treatment. Axial grooves at the impeller inlet are shown to be an effective method of improving the surge margin with a limited effect on efficiency, whilst working within a package restricted design space.

Aortic dissections, which split the aorta into a true lumen (TL) and a false lumen (FL), represent a serious medical condition, affecting otherwise healthy young people with an incidence between 5,000–10,000 cases per year in the United States and 3000 in Europe [1]. A recent study of the outcome of acute type III/ Stanford B aortic dissections (dissections confined to the descending aorta, B-AD) revealed that the long-term prognosis after hospital discharge of patients with B-AD is heterogeneous, with reported survival rates ranging from 56 to 92% at 1 year and from 48 to 82% at 5 years [2]. A partially thrombosed FL, results in a 2.7-fold increase in risk of death [3]. In a recent ex-vitro study, Tasi et al. investigated a chronic aortic dissection in three models [4]. The largest FL diastolic pressure was observed for the model simulating patients with partial false lumen thrombosis and occlusion of the distal entry tear. This study demonstrated that pressure differences between TL and FL are dependent on the geometry of the particular aortic dissection and the location and size of entry tears. A computational fluid dynamics (CFD) study on the effects of entry and exit tear coverage in B-AD based on a patient-derived geometry reported similar results [5]: In particular, occlusion of the exit tear caused increase FL pressure. Simulating thoracic endovascular repair (TEVAR) by occluding the entrance tear depressurized the FL. The capability of CFD to virtually simulate surgical interventions makes it an appealing method for use in pre-surgical planning. For general acceptance however, validation of the simulated results is needed. Catheter measurements of the pressures in the TL and FL are feasible but not very practicable as insertion of a catheter in the FL through the entry or exit tear bears unjustifiable risk to the patient. More recently, 7D phase contrast magnetic resonance imaging (pcMRI) methods (3 spatial directions, 3 velocity directions and time equal 7 dimensions) have been introduced that allow the acquisition of the 3D velocity field at several time points in the cardiac cycle, thereby providing information that can be directly compared with the velocity field simulated with CFD. Due to the large duration of the image acquisition, compromises in temporal and spatial resolution are made which need to be considered when performing such a comparison. Here we present a method based on interpolating the simulated velocity field onto a structured grid employing direct interpolation and spatial Fourier Fast Transformation (FFT) to replicate artifacts as they are present in the 7D pcMRI data. The interpolated velocity components are the then qualitatively compared using image correlation analysis.

This dissertation focuses on a Computational Fluid Dynamics (CFD) study of offshore floating structures, particularly floating Wave Energy Converter (WEC) devices. The open-source CFD software, OpenFOAM®, is evaluated for its effectiveness in simulating relevant phenomena. The study presents the hydrodynamic analysis and optimization of a novel axisymmetric single cylindrical WEC equipped with a moonpool, called MoonWEC. The primary aim is to optimize the design of a small-scale model of the MoonWEC device by minimizing pitch rotations, enhancing heave motion, and facilitating its moonpool oscillations using CFD. A set of new laboratory experiments was conducted to characterize the hydrodynamic response of the device. These experiments were numerically reproduced in OpenFOAM. A detailed explanation of the numerical setup in OpenFOAM is provided in the thesis for the readers to reproduce the CFD model for any moored floating structure. The heave and pitch responses were analyzed by comparing experimental and numerical data, showing good agreement. The results showed that the MoonWEC device can achieve the preferred excitation in heave, but it can also undergo the unpreferred excitation in pitch. By shifting the centre of mass, MoonWEC was numerically optimized to reduce the pitch rotations without affecting the heave oscillations. The moonpool motion was also analyzed for the optimized small-scale model. The study concludes that the CFD model in OpenFOAM, coupled with the MooDy library, can accurately simulate the hydrodynamics of the MoonWEC. The optimization study shows that the centre of mass of the device is a key parameter in controlling the natural period of the device in pitch. The analysis of the moonpool shows that the MoonWEC has the potential to generate significant power. This research contributes to the ongoing efforts to develop wave energy as a sustainable and renewable energy source.

CFD studies of dynamic gauging