Reduction In Drag Coefficient Research Articles

Research on Energy Loss of Optimization of Inducer–Impeller Axial Fit Dimensions Based on Wave-Piercing Theory

With the development of modern fluid machinery, the energy density of pumps is gradually being improved, and at the same time, higher demands are being placed on the cavitation performance, hence the introduction of the inducer and centrifugal impeller to form a dynamic–dynamic series structure. However, there are strict constraints on the axial size of pumps in fields such as firefighting and aerospace. The traditional empirical formula no longer satisfies the need to fit the axial dimensions between the induced wheel and the impeller at high velocities. Therefore, based on the wave-piercing theory, the drag reduction coefficient is introduced to explore the optimal axial fit size from the perspective of energy characteristics. This paper focuses on the influence of the inducer’s wake on the energy characteristics of downstream impellers, and conducts the following research: by adjusting the axial matching dimensions between the upstream inducer and the centrifugal impeller in the initial model, ten sets of axial distance models with matching dimensions of KD are designed, and the drag reduction coefficient is embedded to determine the optimal axial distance. The results show that the optimal axial distance is 0.2D, which is far lower than the axial distance value of 0.42D obtained from the traditional empirical formula for axial matching dimensions. Meanwhile, this paper uses tangential velocity, the inlet flow angle of the impeller, entropy production theory, and other indicators to analyze the internal energy loss of the high-speed vehicular fire pumps one by one. All of them confirm that the impeller in the high-speed vehicular fire pump has the lowest energy loss and optimal performance at an axial distance of 0.2D. Specifically, at this axial distance, the head can reach 259 m, and the hydraulic efficiency is as high as 83.62%. Thus, the feasibility of determining the axial placement of the impeller using the drag coefficient is validated. This research provides new insights into determining the axial coordination dimensions between the inducer and the impeller.

Reduction of Drag Coefficient Due To Misaligned Wind‐Waves

AbstractRecent field observations suggest that the air‐sea momentum flux (or the drag coefficient) is significantly reduced when the dominant wind‐forced surface waves are misaligned from local wind. Such conditions may occur under rapidly changing strong winds (such as under tropical cyclones) or in coastal shallow waters where waves are refracted by bottom topography. A recent Large Eddy Simulation (LES) study also shows that the drag coefficient is reduced by a misaligned strongly forced wave train (with a small wave age of 1.37). In order to investigate more realistic field conditions, this study employs LES to examine the effect of a misaligned (up to 90°) surface wave train over a wide range of wave age up to 10.95. For all wave ages examined, the drag coefficient is reduced compared to the flat surface condition when the misalignment angle exceeds around 22.5°–45°. The drag reduction may occur even if the form drag of the wave train is positive.

A Mesh-Based Approach for Computational Fluid Dynamics-Free Aerodynamic Optimisation of Complex Geometries Using Area Ruling

In this paper, an optimisation procedure is introduced that uses a significantly cheaper, and CFD-free, objective function for aerodynamic optimisation than conventional CFD-driven approaches. Despite the reduced computational cost, we show that this approach can still drive the optimisation scheme towards a design with a similar reduction in drag coefficient for wave drag-dominated problems. The approach used is ‘CFD-free’, i.e., it does not require any computational aerodynamic analysis. It can be applied to geometries discretised using meshes more conventionally used for ‘standard’ CFD-based optimisation approaches. The approach outlined in this paper makes use of the transonic area rule and its supersonic extension, exploiting a mesh-based parameterisation and mesh morphing methodology. The paper addresses the following question: ‘To what extent can an optimiser perform (wave) drag minimisation if using ‘area ruling’ alone as the objective (fitness) function measurement?’. A summary of the wave drag approximation in transonic and supersonic regimes is outlined along with the methodology for exploiting this theory on a typical CFD surface mesh to construct an objective function evaluation for a given geometry. The implementation is presented including notes on the considerations required to ensure stability, and error minimisation, of the numerical scheme. The paper concludes with the results from a number of (simple and complex geometry) examples of a drag-minimisation optimisation study and the results are compared with an approach using full-fidelity CFD simulation. The overall conclusions from this study suggest that the approach presented is capable of driving a geometry towards a similar shape to when using full-fidelity CFD at a significantly lower computational cost. However, it cannot account for any constraints, driven by other aerodynamic factors, that might be present within the problem.

Thermal inspection of hybrid nanofluid flows over a stretched cylinder at an oblique stagnation point with variable characteristics

AbstractThe enhanced thermal characteristics of hybrid nanofluids make them more versatile compared to conventional fluids. These improved thermal properties render hybrid nanomaterials highly practical for a wide range of applications, including solar systems, energy production, and cooling processes. In line with this perspective, the current study concentrates on evaluating the thermal performance of two unique hybrid nanofluid flows that impinge obliquely on a stretched cylinder. Two base fluids, FC‐77 and a binary mixture of water and ethylene glycol (50:50)%, have been considered, with the addition of nanoparticles such as single‐walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). The said model's novelty is enhanced by the temperature dependent viscosity and thermal conductivity. Appropriate transformations are applied to derive a system of ordinary differential equations (ODEs), which are then solved numerically using the bvp4c method. A thorough examination is conducted on the physical phenomenon of pertinent parameters, accompanied by graphical representations. The results revealed that, for the FC‐77 coolant‐based hybrid nanofluid, mounting the particle volume fraction leads to a significant reduction in temperature distribution. Additionally, it is perceived that the presence of a variable viscosity parameter causes a reduction in the surface drag coefficient as well as the axial and tangential velocities. The validity of the proposed flow model is demonstrated by comparing the results with those from an earlier study.

Aerodynamic shape optimization using design-variables-screening method

Aerodynamic shape optimization involving a complex geometric model or problem may have tens or hundreds of design variables, necessitating multiple accurate but time-consuming computational fluid dynamics simulations to produce optimal designs, which greatly affects the efficiency of optimization and. To address this challenge, this article proposes an efficient optimization method based on design-variables-screening. Within the framework of the method, a complicated input–output relationship is broken down into quantitative effects. The influence of design variables on the objective function is calculated by the Kriging regression model and functional analysis of variance. In the meantime, a screening strategy is proposed to facilitate the selection of design variables for optimization. The less important design variables in the problems of interest are fixed so that the dimensionality of the problems is reduced to save computational cost. Experimental results on the National Advisory Committee for Aeronautics airfoil (NACA0012) demonstrate that the simplified model with the screening strategy achieves nearly the same reduction in drag coefficient as the conventional method that optimizes all design variables. Moreover, it significantly enhances the efficiency of optimization and contributes to the enhancement of flow stability.

Aerodynamic drag improvements on a circular cylinder using passive Venturi actuators

Scale-adaptive simulations (SAS) of three-dimensional flow around a circular cylinder fitted with a passive version of a novel flow control method (passive Venturi actuator, PVA) are performed at a diameter-based Reynolds number of Re = 28 000. The PVA consists of one or more narrow slits located at the top and/or bottom sides of the cylinder that connected to the throat of the axial Venturi slit in this cylinder. The main purpose of the study is to investigate the influence of divergence angle and narrow slit location relative to the axial Venturi slit on the aerodynamic performance of the cylinder. To this end, four models were designed with various PVAs. Additional models, a plain cylinder (unmodified model) and a cylinder fitted with an axial Venturi slit (model without a narrow slit), were also used for quantitative comparison. SAS predicts that an additional 5% reduction in the time-averaged drag coefficient, ⟨CD⟩, was observed when two narrow slits located on the surface at an angle of ±80° from the front stagnation line were fitted to the cylinder with an axial Venturi slit. Reducing the divergence angle of the PVA leads to improvements in ⟨CD⟩ and root mean square of fluctuating force coefficients, CD−rms and CL−rms. It is found that a cylinder with a PVA that has two narrow slits and a divergence angle of 6° can produce a 28.6% reduction in ⟨CD⟩, a 58.5% reduction in CD−rms, and an 81.2% reduction in CL−rms, when compared to the plain cylinder.

Optimizing flow control with deep reinforcement learning: Plasma actuator placement around a square cylinder

This study introduces a deep reinforcement learning-based flow control approach to enhance the efficiency of multiple plasma actuators on a square cylinder. The research seeks to adjust the control inputs of these actuators to diminish both drag and lift forces on the cylinder, ensuring flow stability in the process. The proposed model uses a two-dimensional direct numerical simulation of flow past a square cylinder to represent the environment. The control approach involves adjusting the AC voltage across three specific configurations of the plasma actuators. Initially tested at a Reynolds number (ReD) of 100, this strategy was later applied at ReD of 180. We observed a 97% reduction in the mean drag coefficient at ReD = 100 and a 99% reduction at ReD = 180. Furthermore, the findings suggest that increasing the Reynolds number makes it harder to mitigate vortex shedding using plasma actuators on just the cylinder's rear surface. However, an optimized configuration of these actuators can fully suppress vortex shedding under the proposed control scheme.

Spacing effects on blast loading characteristics of two tandem square columns under planar shock waves

To effectively evaluate the structural responses, it is crucial to possess relevant knowledge regarding the blast load on the structure. The loading characteristics of two columns differ from those of a single column due to complex flow-field interference. The spacing effect on blast loading characteristics of two tandem rigid square columns is examined numerically and experimentally for different center spacing between the columns (L = 1.2B–12B, where B represents the side length of a column). This includes studying drag characteristics, distribution patterns of reflection overpressure and impulse, and understanding the physical mechanism under blast load. The experimental tests use a shock tube device powered by high-pressure gas, while numerical simulations solve Euler equations using computational fluid dynamics techniques. Our findings reveal that spacing cases can be categorized into four situations: small and medium spacings (L/B = 1.2–2 and 2.5–4), where the upstream column exhibits a significant shielding effect on the downstream column, resulting in the reduced drag coefficient for the downstream column; large spacings (L/B = 5–7), where drag coefficient improves but remains lower than that of a single column; superlarge spacings with negligible shielding effect (L/B = 8–12), leading to similar blast loading for the downstream column compared to a single column.

Wind tunnel experimental study of aerodynamic characteristics of co-flow jet wing with built-in air source

To further investigate the aerodynamic characteristics and control mechanisms of co-flow jet wings, this study presents the design of a co-flow jet wing (CFJ-CLARKY18) with an embedded micro centrifugal compressor. The CFJ-CLARKY18 wing, based on the CLARKY18 airfoil, incorporates a miniature centrifugal compressor positioned horizontally within the wing's cavity, with its rotor axis perpendicular to the wing chord line, thus alleviating geometric constraints and the compressor's exhaust swirl. The integration of the co-flow jet device with the wing is achieved through a split-flow channel design to ensure uniform co-flow jet injection, followed by verification of jet uniformity and calibration of six jet momentum coefficients. Subsequently, static and dynamic control experiments of the co-flow jet wing are conducted in an open-return wind tunnel, utilizing force measurement systems and high-speed particle image velocimetry tools to investigate its aerodynamic characteristics and control mechanisms. Static stall tests indicate that, compared to the original wing, the CFJ-CLARKY18 wing exhibits a significant increase in lift and a noticeable delay in stall angle. At low angles of attack, an increase in co-flow jet momentum leads to a reduction in drag coefficient, with the possibility of achieving negative drag (thrust) even at high co-flow jet momentum coefficients. The results of dynamic stall tests with force measurements indicate that, while keeping the reduced frequency constant, an increase in co-flow jet momentum coefficient results in higher maximum lift and average lift coefficients, accompanied by a significant reduction in average drag coefficient and the hysteresis loop area of the lift coefficient. Despite the increased reduced frequency exacerbating the wing's stall effect, the stall effect weakens significantly once the co-flow jet momentum coefficient is increased.

A New Circular Section Control for Streamwise Profiles in Aeroengine Nacelle Cowl Design and Optimization

Nacelle cowl design is dedicated to generating a three-dimensional surface with optimal drag performance. Most previous approaches focused primarily on the design method driven by streamwise profiles, which introduced no additional aerodynamically significant variables into the geometric constraints. Therefore, to explore more design spaces for drag reduction of the nacelle cowl, this paper proposes a design refinement method by adding a circular curve that passes through the locations of maximum thickness of given streamwise profiles at various angles toward the nacelle axis, which are regarded as the design variables. A proof-of-concept study was modeled using a combination of computer aided design, Latin hypercube sampling, computational fluid dynamics (CFD) simulation using Reynolds-averaged Navier–Stokes equations closed by a k-ω shear stress transport model, and a kriging surrogate model, in order to search for the optimal solution in design space. The result of optimization shows that the aerodynamic performance of the nacelle cowl was optimized significantly, with a 28.50% drag coefficient reduction with only three angular variables taken to create the design space, illustrating the feasibility of the proposed approach.

The Impact of Observed Drag Reduction Over Land on Typhoon Forecasting

AbstractThe surface drag coefficient plays a crucial role in determining the momentum exchange between the Earth's surface and the atmosphere. Previous studies have observed a tendency for the drag coefficient to decrease at high wind speeds over land, primarily due to the inverse energy cascade. This study aims to examine the impacts of the reduced drag coefficient on the typhoon forecasting skills in terms of the track, the central pressure, and the 10‐m maximum wind speed. Drag reduction is approached through the logarithmic wind profile and a new formula that considers the reduction in roughness length. The results show that the track and the 10‐m maximum wind speed forecasts are improved, but these improvements are primarily evident over plain areas, as the typhoon structure is significantly disrupted by the topography over mountainous areas. Additionally, the reduced drag coefficient results in less dissipation of the typhoon's wind fields over land. As the wind speeds at coastal areas are enhanced compared with those in operational model, the changes in the Coriolis force are responsible for the track prediction improvement. These findings highlight the importance of parameterizing coherent processes in current numerical models.

Investigation of the effect of nose shape and geometry at supersonic speeds for missile performance optimisation

This paper investigated and analysed the influence of the missile nose shapes and geometry on the drag force coefficients at supersonic Mach numbers ranging from 2 to 5. The nose shape investigation includes a pointed cone, pointed ogive, and blunt cone with a constant length and diameter of cylindrical afterbody. Subsequently, the nose length was manipulated to investigate how the nose geometry with different fineness ratios affected each drag component. The drag force coefficient and its components were determined using a program called MATLAB_Aerody, in which a semi-empirical approach was implemented for the calculations. The program was validated against the semi-empirical results with existing theoretical and experimental results. The comparison showed a maximum error of 3.6%. The results of the nose shape analysis show that a sharper and more slender nose with a pointy tip produces a minimal drag. Nose bluntness, however, creates considerable additional drag force due to a higher wave drag coefficient by forming detached or bow shock waves. At supersonic speeds, increasing the fineness ratio significantly reduces the drag force by drastically decreasing the wave drag coefficient with a marginal increase in the skin friction coefficients. However, the results show an insignificant additional gain for the skin friction drag and a reduction in the wave drag coefficient when the nose has a fineness ratio beyond 4.5. Furthermore, the results from both analyses show that the base drag coefficient is invariant with the nose shape and the fineness ratio. Therefore, a better missile performance can be achieved with a sharper and more slender nose shape with a higher fineness ratio.

Impact of Stefan flow on the interphase scalar transfer in flow past random particle arrays

By using a particle-resolved direct numerical simulation, the impact of Stefan flow on interphase heat transfer in flow past static random particle arrays is investigated. The findings demonstrate that the temperature boundary layer of particles is thickened/thinned by the outward/inward Stefan flow and therefore hinders/improves the contact between main gas flow and particles. With the impact of positive Stefan Reynolds number (Resf), the maximum percentage reduction of Nusselt number could be over 3 times of the maximum percentage reduction of drag coefficient at the same condition. The rise in particle Reynolds number (Re) or solid volume fraction (c) can partially offset the impact of Stefan flow. Finally, the simulation data are used to develop a correction factor for interphase heat transfer considering the impact of Stefan flow for −3 < Resf < 6, 0 < Re < 100, and 0 < c < 0.5. Note that the scalar in current work is chosen to be the dimensionless temperature, but the results are general and applicable to any passive scalar.

CFD Simulation of Aerodynamics Truck Using Cylinder as Drag Reduction Device

Reducing drag is an excellent approach to improving truck efficiency and saving fuel. The addition of the cylinder could be an alternative for drag reduction devices like the windshield that has a similar function to enhance the truck’s aerodynamic performance. A numerical analysis was performed using Ansys Fluent CFD software to estimate the influence of the cylinder on the truck's drag force. The study was conducted by comparing truck without additional cylinder above the truck’s head, truck with windshield, and truck with cylinder variations, which round, type-I, and type-D cylinders. In the simulation, the analysis was carried out at a velocity of 30 m/s using the k-epsilon turbulence model. A grid independence test was conducted to minimize errors and optimize iteration time. The simulation results showed that using round, I-type, and D-type cylinders as an alternative to the windshield reduced the truck's drag coefficient, with the D-type cylinder achieving the highest reduction in drag coefficient, which is 0.72. Modifications in the design of the drag reduction cylinder can lower fuel consumption indirectly by 6.95 % using a D-type cylinder.

Artificial intelligence control of a low-drag Ahmed body using distributed jet arrays

This work proposes a machine-learning or artificial intelligence (AI) control of a low-drag Ahmed body with a rear slant angleφ = 35° with a view to finding strategies for efficient drag reduction (DR). The Reynolds numberReinvestigated is 1.7 × 105based on the square root of the body cross-sectional area. The control system comprises of five independently operated arrays of steady microjets blowing along the edges of the rear window and vertical base, twenty-six pressure taps on the rear end of the body and a controller based on an ant colony algorithm for unsupervised learning of a near-optimal control law. The cost function is designed such that bothDRand control power input are considered. The learning process of the AI control discovers forcing that produces aDRup to 18 %, corresponding to a drag coefficient reduction of 0.06, greatly exceeding any previously reportedDRfor this body. Furthermore, the discovered forcings may provide alternative solutions, i.e. a tremendously increased control efficiency given a small sacrifice inDR. Extensive flow measurements performed with and without control indicate significant alterations in the flow structure around the body, such as flow separation over the rear window, recirculation bubbles and C-pillar vortices, which are linked to the pressure rise on the window and base. The physical mechanism forDRis unveiled, along with a conceptual model for the altered flow structure under the optimum control or biggestDR. This mechanism is further compared with that under the highest control efficiency.

Policy transfer of reinforcement learning-based flow control: From two- to three-dimensional environment

In the current paper, the zero-mass synthetic jet flow control combined with a proximal policy optimization (PPO) algorithm in deep reinforcement learning is constructed, and a policy transfer strategy which is trained in two-dimensional (2D) environment and migrated to three-dimensional (3D) environment is proposed and analyzed. By policy, we mean the flow control strategy of the agent learned by interacting with environment through deep reinforcement learning (DRL) algorithm. Through comprehensive evaluations of vortex separation in the cylindrical boundary layer and wake region at different Reynolds (Re) numbers, the PPO model trained in the 2D environment can reduce the drag coefficient by approximately 6.3%, 18.6%, and 23.7% at Re = 100, 200, and 300, respectively, when the spanwise length of the 3D environment is equal to the cylinder's diameter. Moreover, when the spanwise length is three times the diameter, the drag reduction capability is about 5.8%, 15.4%, and 13.1% at the three Re numbers, respectively. Additionally, the PPO model trained in the 2D environment also demonstrated outstanding migration learning capability in a new 3D flow field environment with varying Re numbers, successfully suppressing vortex shedding and reducing drag coefficient. Furthermore, the results illustrate that the model trained at high Re numbers could still reduce the drag coefficient in the 3D environment with low Re numbers, while the model trained at low Re numbers was not as effective at achieving drag reduction in the environments under high Re numbers. Overall, the proposed policy transfer strategy has been proven to be an effective method applying DRL agent trained in 2D flow to a new 3D environment.

Enhancing the Dynamic Stability of Pylons via Their Drag and Lift Coefficients by Finite Volume Method

This study aimed to estimate the drag and lift coefficients of the long-span bridge pylon using the finite volume method (FVM). The k-ω turbulence model was applied to analyze the behavior of wind flow around the pylon, yielding drag and lift coefficient values with an error of 0.98% compared to a previous tunnel experiment. Four recommended cross-sections were proposed to reduce drag and lift forces acting on the pylon, including concave, convex, crossing, and chamfering cross-sections. The finding indicated that drag and lift coefficient decreased for all cross-sections. Cutting edges of concave, convex, and chamfering cross-sections with a ratio ranging from 0.2 to 0.3 has the greatest impact on reducing drag coefficient, while the crossing cross-section with a cutting ratio ranging from 0.2 to 0.25 has the lowest drag coefficient. The maximum reduction in drag and lift coefficients were 23.69% and 13.14% for concave and chamfering cross-sections. Thus, cutting edges of cross-sections is an effective method to enhance the aerodynamic stability of the pylon. Additionally, we evaluated drag and lift coefficients for different wind direction angles. The angles of 0, 30, and 90 degrees resulted in the highest drag coefficient, while the angle of 0 degrees and the angle of 90 degrees resulted in the lowest and highest lift coefficient, respectively. This study not only provides recommendations for cross-sections that reduce forces acting on the pylon but also provides the intensity of this reduction through corresponding estimation equations. In conclusion, concave and chamfering cross-sections are the most effective in reducing drag and lift coefficients, or, in other words, increasing the aerodynamic stability of the pylon.

The Influence of Traffic Wakes on the Aerodynamic Performance of Heavy Duty Vehicles

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Road vehicles have been shown to experience measurable changes in aerodynamic performance when travelling in everyday safe-distance driving conditions, with a major contributor being the lower effective wind speed associated with the wakes from forward vehicles. Using a novel traffic-wake-generator system, a comprehensive test program was undertaken to examine the influence of traffic wakes on the aerodynamic performance of heavy-duty vehicles (HDVs). The experiments were conducted in a large wind tunnel with four primary variants of a high-fidelity 30%-scale tractor-trailer model. Three high-roof-tractor models (conventional North-American sleeper-cab and day-cab, and a zero-emissions-cab style) paired with a standard dry-van trailer were tested, along with a low-roof day-cab tractor paired with a flat-bed trailer. Amongst these, trailer variants provided a total of 10 HDV configurations that were tested in uniform turbulent flow over a range of freestream yaw angles between ±15°, and with wake effects over a range of yaw angles between -2° and +11°. Up to 53 specific wake-flow conditions were applied to each HDV configuration. Wind-load and surface-pressure measurements were acquired and provide indicators of the manner in which the aerodynamic performance of the HDV models are influenced by traffic wakes.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;Drag-coefficient reductions up to 17% for individual drag-coefficient values and up to 9% for wind-averaged values were observed. Wakes from adjacent-lane vehicles were observed to have comparable, or sometimes greater, influence to those from safe-distance same-lane vehicles. The wakes influence primarily the forward-facing surfaces of the HDV, resulting in performance changes associated with tractor modifications being affected more than for trailer modifications. These results represent the first comprehensive study of traffic-wake effects on HDVs at safe inter-vehicle distances in highway-driving conditions, and highlight potential differences in real-world aerodynamic performance relative to the standard wind-averaged uniform-flow metrics used for fuel/energy-use and emissions predictions.&lt;/div&gt;&lt;/div&gt;

Influence of Porosity on Drag Coefficient of Perforated Road Signs

To ensure the structural stability of road signs against strong gusts of wind, perforated road signs with sign boards perforated at regular intervals have been adopted for use in urban road infrastructure. However, ASCE 7-22 standards do not consider the drag coefficient of signs with low porosity, i.e., less than 30%. Therefore, here, computational fluid dynamics (CFD) analysis was performed to analyze the drag coefficient of perforated road signs with a porosity of less than 30%. The aspect and clearance ratios, which are the width/height ratio of a perforated road sign and the height of the perforated road sign/its distance from the ground, respectively, were set as parameters. Subsequently, the drag coefficient of perforated road signs with a porosity of 30% was calculated, and the effect of porosity and wind speed on the drag coefficient of perforated road signs was analyzed. Results show that the drag coefficient of perforated road signs decreased as the porosity increased, with a drag coefficient reduction effect of up to 0.85 times. Furthermore, perforated road signs with a high clearance ratio exhibited significant decreased drag coefficient. For perforated road signs, the drag coefficient does not show a clear correlation with wind speed.

Two-dimensional hydrofoil hydrodynamic performance and waveform evolution studies in density stratification and homogeneous fluid

This paper presents a numerical simulation study of the hydrodynamic coefficients, surrounding flow and generated internal waves of the NACA0012 hydrofoil in two-dimensional unsteady incompressible viscous stratified and uniform flows using computational fluid dynamics (CFD) methods. The Reynolds-averaged Navier-Stokes equations are discretized using the finite volume method (FVM) and combined with the volume of fluid (VOF) method to capture the interface between different phases. The k-ω SST turbulence model is used to predict the turbulent flow around the hydrofoil under different conditions. In order to validate the numerical methods, the simulation values are compared with the experimental results in this paper. The hydrodynamic coefficients and generated flow fields of hydrofoils in a stratified flow environment, i.e. water velocities, angles of attack, freshwater layer thicknesses, density differences and submergence depths are investigated. The surrounding flow fields and hydrodynamic characteristics of the hydrofoil in stratified flow are revealed by comparing the force coefficients and flow fields in homogeneous flow environment. The results show that compared to uniform flow, the hydrofoil can have a maximum loss of lift coefficient of 10.29% and a maximum reduction in drag coefficient of 49.1% in a stratified flow environment. Choosing the right variable can significantly improve the lift-to-drag ratio.