CFD Techniques Research Articles

Comprehensive numerical modeling analysis and experimental validation of a multi-turn pulsating heat pipe

The aim of this paper is to present the results of the experimentally validated numerical code designed for thermal-fluid computations in pulsating heat pipes using CFD techniques. The analysis was carried out using the OpenFOAM software, where an algorithm was developed to simulate multiphase flow with phase change and coupled heat transfer between the fluid and solid domains. The article meticulously delineates the steps involved in implementing and validating the model, commencing from basic comparative tests like the Stefan problem, progressing through Scriven’'s bubble growth, and culminating in an experiment with single- and multi-turn pulsating heat pipes. The algorithm has been refined by including a convergence criterion based on the Galusinski-Vigneaux number, which allows faster results and reduces the likelihood of numerical anomalies. Finally, an experiment was carried out to evaluate the thermal efficiency of a two-loop heat pipe on a specially designed experimental set-up constructed by the authors. In the experiment, ethanol was utilized as the working fluid, operating within a temperature range of 20 to 90 °C. The experiment was carried out with three distinct filling ratios: 50 %, 62.5 %, and 75 %. The validated parameters included pressure and temperature at the measurement points and the experimentally derived thermal efficiency results were compared with the numerical results. The model showed an error of 7.06 ± 3.73 %.

Analysis of thermo-hydraulic flow and optimisation heat augmentation in 3D dimpled pipe based on design of experiment method and Taguchi technique evaluation

In this work, the numerical analysis concentrates on investigating thermal flow patterns, pressure drops, varying velocity components and heat transfer behaviour. Impacts of four parameters on the enhancement of thermohydraulic performance are carried out using three-dimensional calculations employing CFD techniques: different spacing, diameter, number and distance for dimples were investigated. Additionally, utilising a design of experiments (DoE) strategy together with the Taguchi technique (TT) and response surface methodology (RSM), the impacts of the factors listed below are optimised. The results indicated that the different flow fields and heat transfer patterns were because of the use of depressions on the tube's inner surface. A comprehensive flow investigation with the dimple and tube wall was established to explain the mechanism of pressure drop and heat transfer change. The results of orthogonal experiments show that the optimal design of the spiral tube in this investigation using computational fluid dynamics using DoE, RSM and TT has a temperature difference and heat transfer coefficient of about 35.75% and 36.1% higher improved pipes. The results show a high PEF value greater than 1. According to the above results, various design applications require flow hydrodynamic analysis and heat performance enhancement.

Simulation analysis and optimization of containerized energy storage battery thermal management system

The air-cooling system is of great significance in the battery thermal management system because of its simple structure and low cost. This study analyses the thermal performance and optimizes the thermal management system of a 1540 kWh containerized energy storage battery system using CFD techniques. The study first explores the effects of different air supply angles on the heat transfer characteristics. Second, the evaluation indexes of heat removal efficiency, air exchange efficiency, temperature and velocity uniformity coefficient are used to select the optimal air supply angle by the Topsis method. Then, the return air vent position is optimized based on the optimal air supply angle, and the optimal solution is obtained. Research indicates that increasing the air supply angle enhances air mixing within the container and simultaneously decreases the battery pack surface temperature. With a 90° air supply angle, the maximum temperature reduces to 33.58 °C, a 19.52 % reduction compared to 30°. The temperature difference across each battery surface also drops by 16.02 % to 3.46 °C. Adjusting the position of the return air vent further improves temperature uniformity and air flow distribution within the battery compartment. When the air supply angle is 90° and the return air vent evenly distributed at Z = 0.85 m next to the fire door, an optimal uniform temperature distribution is achieved. This reduces the maximum surface temperature by 16.47 %, from 36.67 °C to 30.63 °C and decreases the average temperature difference to 3.0 °C, 21.4 % lower. Thus, the present method effectively enhances the performance of the containerized energy storage battery thermal management system.

Three-Dimensional Numerical Studies on Optimizing the Discharge Coefficient of Screech Holes Resembling that of an Afterburner Using CFD Technique

Three-Dimensional Numerical Studies on Optimizing the Discharge Coefficient of Screech Holes Resembling that of an Afterburner Using CFD Technique

Innovative Implementation of Computational Fluid Dynamics in Proteins Denaturation Process Prediction in Goose Breast Meat and Heat Treatment Processes Optimization

This study aimed to calculate the optimal thermal processing parameters for goose meat using CFD simulation. CFD provides a precise determination of heat treatment conditions by predicting protein denaturation and mass loss, leading to higher quality and improved sensory experience and, thus, acceptance of products. Accurate calculation of these conditions reduces energy losses and enhances process efficiency in the food industry. This study focused on the prediction of protein denaturation and cooking loss in goose breast meat during roasting. Specific CFD techniques, including conjugate heat transfer and phase change models, were utilized to ensure accuracy in protein denaturation prediction. These models accounted for variations in meat composition, such as fat and water content across different samples, which improved the accuracy of the predictions. Optimal conditions were determined using a mathematical model. These conditions were 164.65 °C, 63.58% humidity, and a fan rotation of 16.59 rpm for 2000 s. The myosin, collagen, and actin denaturation levels, as well as cooking loss, closely matched predicted values. The findings show that CFD is a valuable method for evaluating protein denaturation and cooking loss in goose breast meat, potentially improving product quality and consistency in gastronomy and the meat industry. This innovative optimization method enhances food production efficiency and elevates sensory characteristics, physicochemical properties, and nutritional value, contributing to consumer satisfaction and market competitiveness. The model proposed in this paper can be adapted to predict denaturation in other types of meat or food products with necessary modifications, offering broad applicability. Potential limitations of using CFD in protein denaturation prediction in complex food matrices include the need for detailed compositional data and computational resources, which can be addressed in future research.

Evaluation of tribological performance in contact pairs by implementing the biomimetic surface textures with lubricant flow using CFD techniques

PurposeThis paper aims to investigate the tribological benefits of a biomimetic teardrop surface texture inspired by snakeskin compared to conventional surface textures with the help of geometrical and flow parameters using computational fluid dynamics techniques.Design/methodology/approachThe lubricant is assumed to be Newtonian, and the flow is laminar with constant viscosity and isothermal property. The governing equations, continuity and Navier–Stokes equation, are discretised by the finite volume method, and cavitation modelling is included. The discretisation for the momentum equations is carried out using the second-order difference method for the SIMPLEC algorithm of pressure–velocity coupling.FindingsThe results indicate that biomimetic teardrop surface texturing performs better than conventional shapes surface textures in improving tribological performance. Furthermore, the parallel texture orientation along with the flow generates a high-pressure distribution relative to other orientations. Surface texture area density also highly influences the load-carrying capacity, which is optimum at 29%. Zigzag pattern arrangement performs better compared to linear pattern arrangement of texturing.Originality/valueThe paper proposes that this unique biomimetic teardrop shape can give better tribological performance than conventional shapes.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2024-0053/

On the Features of Numerical Simulation of Hydrogen Self-Ignition under High-Pressure Release

The paper is devoted to the comparative analysis of different CFD techniques used to solve the problem of high-pressure hydrogen release into the air. Three variations of a contemporary low-dissipation numerical technique (CABARET) are compared with each other and a conventional first-order numerical scheme. It is shown that low dissipation of the numerical scheme defines better resolution of the contact surface between released hydrogen and ambient air. As a result, the spatial structures of the jet and the reaction wave that arise during self-ignition are better resolved, which is useful for predicting the local effects of high-pressure hydrogen release. At the same time, the dissipation has little effect on the induction delay, so critical conditions of self-ignition can be reliably reproduced even via conventional numerical schemes. The test problem setups formulated in the paper can be used as benchmarks for compressible CFD solvers.

The Role of Wall Mechanics in the Hemodynamics of a Realistic Abdominal Aortic Aneurysm: A Fluid-Structure Interaction Study

Abdominal aortic aneurysm (AAA) can lead to high mortality rates and further complications such as stroke or heart attack due to the risk of rupture and thrombosis. Wall mechanics play a crucial role in the development and progression of aneurysms. This study investigated the effects of wall mechanics on hemodynamic parameters in AAA to understand the risk of rupture and thrombosis. The impact of three aortic wall models (rigid, linear elastic, and hyperelastic) on structural and hemodynamic parameters was examined using CFD and FSI techniques. The blood was modeled using the Carreau non-Newtonian model, and the flow was simulated using the k-ω model. Physiological pulses were used for the velocity at the inlet and the pressure at the outlet. The results demonstrated close similarity between the predictions of the linear elastic and hyperelastic models, in contrast to the somewhat different results of the rigid model. The hyperelastic model predicted higher deformation and von Mises stress levels than the elastic model, although the difference in stress predictions was smaller than the difference in deformation predictions. The rigid model evaluated the time-averaged wall shear stress and oscillatory shear index higher than the other two models in the aneurysmal area but with a lower relative residence time. In general, the hyperelastic model predicted a higher risk of rupture than linear elastic models and a higher risk of thrombus formation than the other two models. The rigid model had the most optimistic prediction.

Numerical Simulation Study on Flow Field Characteristics and Separation Efficiency of Micro Cyclone by Shunt Ratio

In this study, based on the current situation of waste drilling fluid treatment, the operating parameters of micro cyclones are investigated. A 10-mm micro cyclone used to separate ultrafine particles was designed and the effect of the split ratio on the pressure and axial velocity in the micro cyclone as well as the total separation efficiency was investigated using CFD techniques. The conclusions obtained are that the pressure gradient in the microcyclone increases with the increase of the splitting ratio; the axial velocity decreases with the increase of the splitting ratio; the total separation efficiency increases with the increase of the splitting ratio.

Fast assessment method of annual energy consumption for DSF and SSFs

Double skin façade (DSF) is widely used to improve energy efficiency in buildings. Many studies have analyzed the thermal performance of DSF and single skin façade (SSF) on just standard days or typical moments. However, in order to more accurately analyze its energy-saving effect, its annual thermal performance should be evaluated. For achieving this, a large number of simulations are needed and it is extremely time consuming and complicated. This study provides a new fast calculation method for annual thermal performance and energy consumption of DSF and SSFs. Firstly, based on CFD technique, a simulation method for obtaining indoor temperature of DSF during whole year was established, and the results were verified through experiments. Then, a new simulation calculation method for heating and cooling periods was established, thereby completing annual thermal performance simulation of different facades. Finally, based on total heat gain/loss of each facade, the energy consumption of mentioned facades was calculated, and facades’ various performance can be seen for entire year. As an overall result for Beijing located in cold region, by considering whole year energy consumption, DSF plays as the best one with 18 % energy saving in the whole year compared to the second one which is 3 glazing exterior shading SSF; however, this SSF can save 37 % building area compared to DSF. The result of this study can be useable for other cities with same climate as the Beijing. The analyze method proposed in this study is useable for optimizing building facades in different climates.

Performance Improvement of Two-Phase Steam Ejector based on CFD Techniques, Response Surface Methodology and Genetic Algorithm

Performance Improvement of Two-Phase Steam Ejector based on CFD Techniques, Response Surface Methodology and Genetic Algorithm

Evaluation and Investigation of Hydraulic Performance Characteristics in an Axial Pump Based on CFD and Acoustic Analysis

In this work, the internal flow behaviour and characteristic pressure fluctuations of an axial pump with varying water conditions are analysed. The impact of tip vortex flow on the pattern of turbulent flow is simulated numerically by the application of the CFD technique and experimentally using an acoustics analysis method. The numerical CFD data are verified with an experimental test model for accuracy and reliability. Based on the results, the difference in pressure in the internal flow and at the surfaces of the blade can be impacted through tip leakage vortex regions, which leads to changes in internal flow. Subsequently, the flow in the clearance and tip leakage vortex regions is changed. Moreover, the results reveal that the suction wall upstream is more unsteady near the surface due to more mixing, secondary flow, and tip leakage vortices. Pressure fluctuation occurs near the tip of the blade, caused by the increasing vortex flow velocity and hence raising the turbulent kinetic energy (TKE). Using different monitoring points at the blade impeller reveals high values of the pulsation amplitude. Owing to the region of clearance backflow under low-water conditions, the axial pump displays larger fluctuations in pressure near the tip blade area. Because the leakage flow leaves the gap at a high flow rate, shear layers are formed quickly between the main flow and the leakage flow. Near the end wall, there is a negative-vorticity-induced vortex. Moreover, as the flow rate increases, the pump’s amplitude decreases along with its main frequency. For the low-water flow, the results reveal that there is an important clearance backflow because the axial pump has large clearance.

CFD simulation of methane circulation dynamics in a ventilation installation's tubing

Reducing the risk of occurrence of phenomena such as explosions, as a result of the untimely penetration of a certain amount of explosive gases, inside a ventilation installation, is a priority, regarding the health and safety of workers, material assets and the negative influence on the environment, due to the possible problems caused by the occurrence of explosive atmospheres, formed by mixing air with gases, vapors, mists and combustible dusts. The main measure to prevent explosive atmospheres is to provide adequate ventilation in closed or semi-closed industrial and non-industrial premises. In order to avoid dangerous situations at the level of poorly ventilated ventilation installations where explosive atmospheres can occur, it is necessary to know the behavior of explosive gases as well as their dispersion method. CFD technique was used to study the dynamics of methane circulation inside the piping of a ventilation installation with the help of the ANSYS MULTIPHISICS software package. The paper presents the CFD analysis regarding the influence of the state parameters on the methane flow dynamics inside the ventilation systems. Thus, the state parameters determined in the experimentation area and their introduction into CFD modeling are presented, namely the establishment of the methane flow and dispersion model in ventilation ducts with high complexity.

CFD design of a novel device for temperature profile measurement in Waste-to-Energy plants

Monitoring the flue gas temperature is a crucial issue for Waste-to-Energy (WtE) plants companies, since it is essential to preserve the materials in the post-combustion chamber, the energy efficiency of the plants as well as to control the emissions of pollutants. As of today, the temperature of flue gases in such plants is commonly monitored by means of thermocouples, infrared pyrometers or aspirated thermocouples. However, all these instruments show limitations in terms of accuracy and reliability inside post-combustion chambers. In this paper, the authors present the thermo-fluid dynamics design of a novel device aimed at mitigating the issues of existing technologies, realised by using the modern CFD techniques. Numerical analyses, performed with the open-source OpenFOAM code, allowed to find a suitable shape for the device and to give a first estimate of the measuring errors, which are of the order of 2% (∼26 K at the typical working temperature of WtE plants’ post-combustion chambers).

CFD-based study of inlet flow rate variation on flow field of micro-cyclone

In this study, the operational parameters of the micro-cyclone were investigated. A 10 mm micro-cyclone suitable for waste drilling mud treatment was designed and the effect of the inlet on the flow field within the micro-cyclone as well as the total separation efficiency was investigated using CFD techniques. It was concluded that the pressure gradient inside the micro-cyclone increased with increasing inlet flow; axial and tangential velocities increased with increasing inlet flow; the peak turbulent kinetic energy increased with increasing inlet flow; and the total separation efficiency increased and then decreased slightly with increasing inlet flow.

Approximation of the Couette-Poiseuille flow on an annular domain in compressible regime for a hyperloop pod

Fanno flow is one of the most studied problems in fluid mechanics, as it models the pressure losses on domains in which the characteristic length is considerably lower than the height. These types of flows are present in several applications in the industry, such as pipe flows in pneumatic and hydraulic circuits, oil pipelines or air conditioning and water distribution systems. One potential application can be found in hyperloop design, where flow at high speeds moves between the small gap between the capsule and the tube wall. In this case, the domain is annular-shaped instead of a single cylinder, and the interior wall moves at the capsule speed. Although this quasi-1D flow is strongly affected by the wall friction, it cannot be modelled using the standard Fanno expression. Thus, to model the pressure drop without extensive CFD techniques, a simplified 1D analytical expression is developed to estimate the friction losses. The model assumes a constant ratio between the shear stress on the interior and the exterior walls throughout the channel. Then, instead of the hydraulic diameter as in the standard Fanno expression, a new definition of an equivalent diameter is performed to consider the annular-shaped domain and the movement of the interior wall. The new equivalent diameter is always higher than the original used for Fanno flows (hydraulic one), even twice when the wall speed equals the mean speed. This effect leads to smaller pressure losses due to the movement of one of the walls and indicates that the wall movement is always beneficial. To validate the results obtained from the model, they are compared with an equivalent CFD simulation, leading to a maximum deviation of 5% on the Mach number and 7% on the total friction coefficient.

Review Analysis on CFD Techniques and Numerical Methods for IC Engines Fueled with Diesel and Biofuels

Review Analysis on CFD Techniques and Numerical Methods for IC Engines Fueled with Diesel and Biofuels

Dynamic simulation and analysis of the influence of urethral morphological changes on urodynamics after benign prostatic hyperplasia surgery: A computational fluid dynamics study

Background and objectiveComputational fluid dynamics (CFD) technology has been widely used in medicine to simulate and analyse urine flow characteristics in urology. In previous studies, researchers have modelled the analysis with a simple circular urethra, ignoring the effect of the patient's true urethral morphology on the urinary flow rate. Moreover, the studies tended to be steady-state simulations rather than dynamic simulations. Therefore, this study is established a relatively realistic model of the posterior urethra based on MRI data combined with the urodynamic data of patients and analysed the urodynamic characteristics of the posterior urethra model after benign prostatic hyperplasia (BPH) surgery using a CFD dynamic simulation. MethodsBased on clinical MRI data, a three-dimensional real urethral model was established for two patients with BPH after surgery. The boundary conditions were set according to the patients’ real urodynamic data, and a Reynolds averaged Navier‒Stokes model was used for transient simulations. The dynamic simulation depicted the entire urination process, and the urine flow characteristics were studied under real urethral morphology after surgery. Results1. By comparing the three-dimensional trajectory of urine and the vortex identification cloud map based on the Q criterion, we intuitively observed the distribution of the vortex in the model, and a ‘gourd-shaped’ urethra was more likely to generate a vortex than a ‘funnel-shaped’ urethra. 2. After surgery for BPH, the changes in the posterior urethral pressure were mainly concentrated in the urethral membrane, and the velocity increased while the pressure decreased. The curve of the posterior urethral pressure changes during urination was simulated and calculated. The posterior urethral pressure gradients of the two patients were 6.6 cmH2O and 5.26 cmH2O. ConclusionsThe complete urinary discharge process can be dynamically simulated using CFD techniques. By comparing the simulation results, the posterior urethral morphology can have an important impact on the urinary flow characteristics. Determining the location of vortex generation can lay a foundation for personalized surgical plans for patients in the future. Furthermore, numerical simulations can provide a new method for the study of non-invasive posterior urethral pressure gradients.

Thermal environment optimization in a large space building for energy-saving

As the functionality of large space buildings becomes more sophisticated, to ensure that the interior of the building has a reasonable thermal environment when it is put to use, designers must consider the thermal comfort of the human body and the building's potential for energy-saving during the design stage. The Grand Canal Exhibition Center is used as the research object in this study. Its numerical simulation of two pre-design cases using CFD technique is carried out and it studies the indoor airflow organization and temperature field distribution. In addition, it considers the factors that affect the building's energy consumption and assesses the best case. The Grand Canal Exhibition Center's initial design is optimized using the ADPI index, which is also used to calculate the building's energy-saving and evaluate the whole area's thermal comfort uniformity. The results of the research show that case 2 has greater thermal comfort uniformity and energy-saving potential, with a ground floor ADPI value of 83.3% and uniform thermal comfort throughout the entire zone. The second floor's ADPI value is 85%, and the entire space has the best thermal comfort. The third floor's ADPI value is 79%, and the localized area's thermal comfort is poorer. The building of case 2 has a 5% increase in energy-saving over case 1 regardless of the season, and it still has a significant amount of energy to spare. The research in this paper will be an invaluable resource for architects to design large space buildings.

Numerical simulation of the laminar boundary layer flow over a flat plate

Understanding the dynamic and thermal characteristics of the boundary layer (BL) flows is an essential step toward the best design and operational conditions for many engineering devices. Flow characteristics within the boundary layer are governed by two forces that are in a mutual race to dominate the flow, the viscous and inertial forces. The state of the flow is determined by the relative domination of these two forces inside the boundary layer zone. Theoretical solutions for many BL flow types existed since the beginning of the 20th century. Theoretical solutions are strictly possible for simple boundary layer flow configurations within the laminar range and before flow separation occurs. For practical situations where boundary layer flow problems are prescribed with complex flow configurations, CFD techniques represent the most suitable approach to tackle such types of flows. In this study, the laminar boundary layer flow over a flat plate has been solved numerically leading to a detailed analysis of the boundary layer flow with accuracy comparable to that of the theoretical solution