Search

Purpose This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately. Design/methodology/approach As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases. Findings Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately. Research limitations/implications The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model. Practical implications This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles. Originality/value Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

A new tyre vertical vibration model is proposed for the determination of the tyre vertical mechanical properties. The tyre is simplified as a vibration system composed of several discrete belt elas...

Considering stress constraints in multi-material topology optimization is of great importance from both theoretical and application perspectives. In this article, the stress-constrained multi-mater...

This article proposes two new turbulence models for steady-state and transient-state solutions. For the steady-state solution, by introducing the streamline curvature factor and response threshold ...

Weld of mining dump truck (MDT) frame is prone to fatigue damage due to the unreasonable local structure of cavity with stiffeners. However, there are considerable limitations in the engineering im...

To reduce aerodynamic drag of a minivan, non-smooth surfaces are applied to the minivan’s roof panel design. A steady computational fluid dynamics (CFD) method is used to investigate the aerodynamic drag characteristics. The accuracy of the numerical method is validated by wind tunnel test. The drag reduction effects of rectangle, rhombus and arithmetic progression arrangement for circular concaves are investigated numerically, and then the aerodynamic drag coefficient of the rectangle arrangement with a better drag reduction effect is chosen as the optimization objective. Three parameters, that is, the diameter D of the circular concave, the width W and the longitudinal distance L among the circular concaves, are selected as design variables. A 20-level design of an experimental study using a Latin Hypercube scheme is conducted. The responses of 20 groups of sample points are obtained by CFD simulation, based on which a Kriging model is chosen to create the surrogate-model. The multi-island genetic algorithm is employed to find the optimum solution. The result shows that maximum drag reduction effects up to 7.71% can be achieved with a rectangle circular concaves arrangement. The reduction mechanism of the roof with the circular concaves was discussed. The circular concaves decrease friction resistance of the roof and change the flow characteristics of the recirculation area in the wake of the minivan. The roof with the circular concaves reduces the differential pressure drag of the front and rear of the minivan.

Purpose The purpose of this paper is to develop a numerical model used for calculating the nonlinearities of large-scale hydro-pneumatic suspension (HPS) and investigating the effects of variations in flow path and operational parameter on suspension damping response. Design/methodology/approach To parameterization nonlinearities of the suspension, the author developed a two-phase flow model of a large-scale HPS based on computational fluid dynamics and volume of fluid method. Considerable effort was made to verify the nonlinearities by field measurements carried out on an off-highway mining dump truck. The investigation of effects of variations in flow path and operational parameter on damping characteristics highlights the necessity of the numerical simulation. Findings The two-phase flow model can represent the gas-oil interaction and simulate the suspension operational movement conveniently. Transient numerical simulation results can be used to model the nonlinearities of large-scale HPS accurately. A new phenomenon was discovered that the pressure in rebound chamber presents reduction trend during compression stroke in special cases. It has never been reported before. Originality/value Developed a two-phase flow model of a large-scale HPS, which can manage the gas-oil interaction and capture the complex flow field structure in it. The paper is the first study to model the nonlinearities of a large-scale HPS used in off-highway mining dump truck through transient numerical simulation. Compared with previous researches, such a research not only gives new insight and thorough understanding into the suspension internal fluid structure but also can give good guiding opinions to the optimal design of HPS.

Purpose This paper aims to propose a precise turbulence model for vehicle aerodynamics, especially for vehicle window buffeting noise. Design/methodology/approach Aiming at the fact that commonly used turbulence models cannot precisely predict laminar-turbulent transition, a transition-code-based improvement is introduced. This improvement includes the introduction of total stress limitation (TSL) and separation-sensitive model. They are integrated into low Reynolds number (LRN) k-ε model to concern transport properties of total stress and precisely capture boundary layer separations. As a result, the ability of LRN k-ε model to predict the transition is improved. Combined with the constructing scheme of constrained large-eddy simulation (CLES) model, a modified LRN CLES model is achieved. Several typical flows and relevant experimental results are introduced to validate this model. Finally, the modified LRN CLES model is used to acquire detailed flow structures and noise signature of a simplified vehicle window. Then, experimental validations are conducted. Findings Current results indicate that the modified LRN CLES model is capable of achieving acceptable accuracy in prediction of various types of transition at various Reynolds numbers. And, the ability of this model to simulate the vehicle window buffeting noise is greater than commonly used models. Originality/value Based on the TSL idea and separation-sensitive model, a modified LRN CLES model concerning the laminar-turbulent transition for the vehicle window buffeting noise is first proposed.

The severe additional aerodynamic loads that are generated on a small car when overtaking a coach have an adverse effect on the car handling stability and its safety. In this article, a two-way coupling of the unsteady aerodynamics and multi-body dynamics is performed in order to study the mutual interactions of a car in an overtaking maneuver with a coach. The unsteady aerodynamic interactions are obtained by using SST (Menter) K-Omega Detached Eddy Simulation and overset mesh technology. The aerodynamics couple the multi-body dynamics, taking into account the effects of the transverse spacing and the cross winds. To validate the necessity of the two-way coupling method, a one-way coupling of the aerodynamics to the vehicle motion is also conducted. Finally, by comparing the aerodynamic loads and the dynamic response of the overtaking car in different overtaking maneuvers between one- and two-way coupling, the results show that it should be considered with two-way coupling analyses of the car while overtaking a coach, particularly under the severe conditions of a lower transverse spacing or the crosswinds.

Reducing the sound pressure level (SPL) reliably and effectively is paramount in the presence of uncertainty. Herein, the robust optimisation of a vibro-acoustic system is performed by combining a probabilistic analysis approach and an approximate methodology. A surrogate model containing uncertain variables is established based on the elliptical basis function (EBF) neural network. Using Monte Carlo (MC) simulations, the probability distribution of the output responses are obtained, and the result shows that the sound pressure is influenced by uncertain factors. The simulated annealing (SA) algorithm is adopted to perform the robust optimisation. It shows that the optimisation results not only reduced the SPL inside the passenger car, but also enabled the SPL to be less sensitive to the fluctuations of the uncertain variables.

In this study, vehicle stability under crosswind conditions is investigated. A two-way coupling method is established based on computational fluid dynamics and vehicle multi-body dynamics. Large eddy simulation is employed in the computational fluid dynamics model to compute the transient aerodynamic load, and the accuracy of the large eddy simulation is validated with a wind tunnel experiment. The arbitrary Lagrange–Euler technique is used in the computational fluid dynamics simulation to realise vehicle motion, and a real-time data transmission method is employed to ensure effective exchange of data between the computational fluid dynamics and multi-body dynamics models. The robustness of the two-way coupling model is verified by changing the position of the vehicle centroid. The results of the two-way and one-way coupling simulations demonstrate that crosswinds significantly affect vehicle stability. There is a clear difference between the results obtained with the two methods, particularly after the disappearance of the crosswind. The main reason for the difference is that the interaction between the transient airflow and the vehicle movement is considered in the two-way coupling method. Therefore, investigations of vehicle stability under crosswind conditions should consider the coupling of transient aerodynamic force and vehicle movement.

A feasible method for the estimation of the interval bounds based on strain-life fatigue data is presented. The deviation from each point to the traditional fitting line is considered as the fatigue uncertainty. With groups of different test data points, new strain-life lines are fitted and the expand-root-mean-square-error is introduced as the index of grouped data points. The interval bounds are represented by the covered range of all these lines. Accordingly, the modified interval bounds of four strain-life parameters are obtained. Finally, the fatigue tests on a few samples of three materials are given as examples to show the effectiveness of the method.

Purpose The purpose of this paper is to develop a two-way coupling approach for investigating the aerodynamic stability of vehicles under the combined effect of crosswind and road adhesion. Design/methodology/approach The author develops a new two-way coupling approach, which couples large eddy simulation with multi-body dynamics (MBD), to investigate the crosswind stability on three different adhesion roads: ideal road, dry road and wet road. The comparison of the results obtained using the traditional one-way coupling approach and the new two-way coupling approach is also done to assess the necessity to use the proposed coupling technique on low adhesion roads, and the combined effect of crosswind and road adhesion on vehicle stability is analyzed. Findings The results suggest that the lower the road adhesion is, the larger deviation a vehicle generates, the more necessary to conduct the two-way coupling simulation. The combined effect of the crosswind and road adhesion can decrease a vehicle’s lateral motion on a high adhesion road after the disappearing of the crosswind. But on a low adhesion road, the vehicle tends to be unstable for its large head wind angle. The vehicle stability in crosswind on a low adhesion road needs more attention, and the investigation should consider the coupling of aerodynamics and vehicle dynamics and the combined effect of crosswind and road adhesion. Originality/value Developing a new two-way coupling approach which can capture the complex vehicle structures and the road adhesion with MBD model and the completed fluid filed structure with CFD model. The present study might be the first study considering the coupling of crosswind and low adhesion road. The proposed two-way coupling approach will be useful for researchers who study vehicle crosswind stability.

The influence of transient aerodynamics on a vehicle in a crosswind and the effect on the vehicle’s motion are investigated by employing fully coupled simulations. The fully coupled method makes the simulation data on the fluid dynamics and on the vehicle dynamics exchange in time. LES are used to investigate the movement of the transient turbulence, and wind tunnel experiments are carried out to validate the numerical method. The vehicle is simplified as a three-degree-of-freedom system which moves in only the horizontal direction. The driver’s reaction is considered when the motion of the vehicle is simulated. The results of fully coupled simulations show that the transient aerodynamic loads have a marked influence on the motion of the vehicle. The transitional method of one-way coupled simulations is also employed to obtain data. The simulation results for the two methods are compared with each other. It is found that there is large difference between the results of the two methods. The maximum side force in fully coupled simulations is about 1.22 times the value obtained by the transitional method, and there is a 0.2 m discrepancy between the peak value of the lateral displacement in fully coupled simulations and the peak value in the transitional method. The results show that the transient aerodynamic loads induced by the unsteady motion of the vehicle have a larger effect on the vehicle’s motion than do the aerodynamic loads from the transitional method. Furthermore, the results also reflect the significance of estimating the transient aerodynamic loads in simulations of the vehicle’s motion.

An energy-based fatigue damage model was used to estimate the fatigue life of a mining truck welded frame. Experimental work including monotonic and strain-controlled cyclic loading was conducted to characterize the base metal and the weld. A dynamic model was created for the whole truck in the ADAMS software to estimate the force histories applied to the frame in different maneuvers over a simulated road. A Finite element (FE) model was generated for the welded frame and the cyclic loading obtained from the dynamic model was applied to the FE model. The FE model was used to find the stress and strain responses, which were then used to calculate the strain energy and the fatigue life. The fatigue life predictions for the frame agreed well with observations of the truck’s in-service failure.

In order to reduce frame redundant weight caused by the traditional experience design and delay the crack initiation occurrences at local positions during early service period, a structural weight and lifetime co-optimization method for frame of a mining dump truck based on Kriging approximation model was proposed. Considered as the most sensitive factor to the frame fatigue life and weight, the thickness of several steel plates was chosen as design variables in terms of un-allowed change of structure shape, while achieving weight reduction and improving fatigue life were together regarded as the optimization targets. An experiment design with 20 sample points obtained by the Latin hypercube sampling method was conducted to figure out the sensitivity of design variables, whose response values were acquired through repeated simulations. Those data were supposed to set up the approximation model constructed based on the Kriging interpolation technique and its fitting precision was certified by comparison of the finite element computational results and the approximation model calculated ones. The non-dominated sorting genetic algorithm II (NSGA-II) was utilized to optimize the thickness of the steel plates based on the approximation model. The tolerance between the results of the simulation and the approximation model was less than 1% when using the optimal design variables and the weight of the optimized frame was lessened by 22.3% while the minimum fatigue life and maximum static stress were only decreased by 3.8% and 4.6%, compared with the initial frame. These optimized results were acceptable for frame lightweight almost without expense of fatigue life and static strength.

In light of the fact that computational results based on commonly used turbulence models are unsatisfactory, a modified LRN $${k-\varepsilon}$$ turbulence model is proposed. The modified concept includes the introduction of the total stress limitation idea and separation-aware model. With the help of this concept, the transport effects of total turbulent shear stress are taken into consideration and the boundary separation is detected. Thus, the model’s ability to simulate laminar-turbulent transition, which is an essential feature of the flow field around vehicles, is improved. The Ahmed model and its corresponding experimental data are introduced to validate and evaluate the modified LRN $${k-\varepsilon}$$ model. Several commonly used turbulence models are also introduced as comparisons. Computations are carried out by the ISIS-CFD flow solver. This work shows that predictions achieved by the modified LRN $${k-\varepsilon}$$ model give a better agreement with experimental data than other solutions.

To investigate the aerodynamic behavior of underbody structure in crosswind conditions, two numerical simulation models have been developed by using computational fluid dynamics method. First, to validate the accuracy of these models, the wind tunnel experiment of model with simplified flat underbody has been designed. The computationally predicted results of realizable k-e model show consistency with experimental data, and the correlation deviation of aerodynamic force is less than 10%. By using such model, the aerodynamic force and flow field of car under steady crosswind are simulated using underbody structure, and the influence on the aerodynamic characteristic has been analyzed. It can be found that the aerodynamic force increased significantly under different yaw angle. The physical mechanism response has been clearly shown by investigating the flow field around car body by vortices visualization technique. The results of this study can be served as a suggestion for studying the vehicle stability of high-speed under crosswind.

Large-eddy simulation method was employed to compute the buffeting noise of a simple deep cavity model. Compared with the results of wind tunnel experiments, the numerical results coincided well with the experimental results, which further validated the correctness of Large-eddy simulation method. Large-eddy simulation method was employed to calculate automobile side-window buffeting noise when the side-window near the driver was partially opened by 25%, and the road test data validated its correctness. The flow field results were loaded to the finite element model to compute dynamic response of the car’s windows, the weak vibration of windows was excited by the air energy exchange between interior and exterior when the car at high speed. Acoustic radiation of window structure, sound pressure levels of field points in the frequency domain, panel acoustic contribution analysis of window structure were obtained by the vibration solution for the windows. The results demonstrated that the noise radiation caused by the windows’ vibration aroused the acoustic response significantly at some certain frequencies, although side-windows buffeting noise dominated in the low frequency domain. The rear window acoustic contribution accounted for the major part of the total pressure. Compared with other three side-windows, the contribution of the partially opened side-window to the total pressure was the greatest.

Flow over an open side window in a car exhibits similar characteristics as the flow over an open cavity. Computational Fluid Dynamics (CFD) simulation over a cavity was done as a benchmark. The unsteady flow simulation was carried out using Scale Adaptive Simulation (SAS) turbulence model. The benchmark results, frequency and sound pressure levels of feedback and resonance modes, all well matched with the experimental data. Then, with the right rear window, for example, the mechanism of the side window buffeting was investigated. The simulation results show that side window buffeting noise is generated by large scale vortices and in low frequency. Furthermore, buffeting noise characteristics under several patterns of side windows opening were also numerically investigated. As a result, rear window buffeting noise is more severe than that of front window when one window open, and combination pattern of side windows open can reduce buffeting noise. To decrease the interior noise and improve car ride comfort, four suppression measures through adding a side window weather deflector at the A-pillars, constructing a cavity at the B-pillars, combination of the front and rear windows and installing a row of square cylinder deflector at the B-pillars were also studied, respectively. In conclusion, certain noise reduction can be achieved through four passive control methods.

In order to improve the fatigue performance of a welded A-type frame in a heavy off-road mining truck, a novel method was presented to implement lifetime and weight collaborative optimization while considering uncertainties in geometry dimension, material properties, and bearing load. The mechanical and cyclic material parameters were obtained from experimental work to characterize the base metal and the weldment. The finite element model of a welded A-type frame was constructed to analyze stress distribution and predict fatigue life, the force time histories of which were acquired from multi-body dynamics simulation. The simulated failure position and fatigue life had a good agreement with the actual results. Then, both structural lifetime and weight were considered as optimization objectives. The thickness of main steel plates and elastic and cyclic material parameters were chosen as uncertain design variables as well as main loads at connection locations. The fifty sample points in the light of Latin hypercube sampling method and its responses calculated by finite element analysis were supposed to build the approximation model based on the Kriging approximation method. After its fitting precision was guaranteed, the non-dominated sorting genetic algorithm II (NSGA-II) was utilized to find the optimal solution. Finally, the fatigue life of a welded A-type frame was increased to 2.40&times, 105 cycles and its mass was lessened by 8.2%. The optimized results implied that good fatigue performance of this welded A-type frame needs better welding quality, lower running speed for downhill and turning road surface, and thicker front plates.

Flow passing a vehicle may lead to the increase of the cabin interior noise level through a variety of mechanisms. These mechanisms include vibrations caused by aerodynamic excitations and re-radiation from the glass panels, exterior noise transmitted and leaked through door seals including gaps and glass edge, and transmission of airborne noise generated by the interaction of flow with body panels. It is of vital importance to predict both the flow fields and the acoustic sources around the vehicle to accurately assess the impact of wind induced noise inside the cabin. In the present study, an unstructured segregated finite volume model was used to calculate the flow fields in which a hexahedron grid is used to simplify the vehicle geometry. A large eddy simulation coupled with a wall function model was applied to predict the exterior transient flow fields. The mean flow quantities were thus calculated along the symmetry plane and the vehicle’s side windows. A coupled FEM/BEM method was used to compute the vehicle’s interior noise level. The total contribution of the interior noise level due to the body panels of the vehicle was subsequently analyzed.

The high aerodynamic noise induced by automotive air conditioning systems has important effects on the ride comfort, and the centrifugal fan is the largest noise source in these systems. It is very important to reduce the aerodynamic noise generated by the centrifugal fan. The flow field and the sound field on the whole centrifugal fan configuration have been carried out using the computational fluid dynamics. Simulation results show that the sound pressure level near the outlet of the centrifugal fan is too high. Based on the relationship between flow characteristics and the aerodynamic noise, four parameters of the centrifugal fan, i.e., impeller blade’s outlet angle θ, volute tongue’s gap t, collector inclination angle β, and rotating speed n, were selected as design variables and optimized using response surface methodology. While keeping the function of flow rate unchanged, the peak noise level is reduced by 8 dB or 10.8%. The noise level is satisfactorily reduced.

Cracks of A-type frame of a mining dump truck have occurred before exceeding structural fatigue design life. In order to accurately predict location of cracks and fatigue life of this component and find the reasons, a fatigue life analysis method combined with experiment and simulation is presented. Compared with the tested peak stress and simulated maximum stress of A-type frame under full loadings, the difference is acceptable so that the accuracy of finite element model of A-type frame is guaranteed. The rigid and flexible hybrid model of whole truck is built to get the stress situation based on modal stress recovery method, taking flexible body of A-type frame into account. Compared with the tested acceleration, the vertical simulated acceleration of the seat is acceptable, which ensures the validity of rigid and flexible hybrid model of this mining dump truck. According to the linear Palmgren–Miner hypothesis and S–N curve, fatigue life of A-type frame is assessed. The results show that the predicted cracks location and fatigue life of A-type frame is well accordance with the practical situation. To extend life of A-type frame, a modified structure is presented in this paper.

This paper is concerned with prediction of heat dissipation effect by establishing a 3d geometric model of the radiator group for a ribbon-tubular radiator of a mining dump-truck. By using the CFD approach the airflow characteristics of the radiator group are numerically calculated, and the resistance characteristic and heat transfer performance are analyzed thus the matching point of the fan is calculated, and the heat transfer performance of the water-side is simulated. Then, according to the relative heat transfer theory, the inlet and outlet water temperature of the radiator group under idling condition is obtained by analytical method. The experiment is done subsequently. The maximum deviation rate between the results of the simulation and the experiment is 6.4%, which can meet the engineering requirement and well predicts the heat dissipate performance of the radiator group. The result indicates that by combining the CFD numerical simulation with the analytical method the heat dissipation of the radiator group can be predicted effectively.

Experimental and numerical investigations are conducted to investigate the noise induced by a subsonic flow over a cavity. Particular attention is focused on the problem of low-frequency pressure oscillations inside the cabins of automobiles with open sunroofs. The mechanisms of buffeting noise are examined by considering a model cavity. Extensive experiments are performed to validate the computational scheme developed in the present study. This computational scheme is used for designing generic deflectors for reducing buffeting noise. Experimental and computational results show that the traditional generic deflector is unable to reduce the buffeting noise when the flow velocity is sufficiently high. However, a vented deflector allows the effective control of the buffeting noise at relatively high flow speeds.

Aiming at precisely predicting fatigue life for frame of the 220t mining dump truck, a fatigue life analysis method is presented, integrating multibody dynamic analysis and finite element method. The force of main joints at frame are measured from the multibody dynamic model, whose road is restructured based on ISO/TC108/SC2N67. According to GB/T27025-2008, the dynamic stress test of the whole truck is implemented to obtain the peak stress of the mainly forced area, which is compared with the simulated stress. It is found out that the error is allowable so that the accuracy of the finite element model is definitely ensured. The quasi-static stress analysis method is employed to acquire stress influence coefficient under unit load, which is associated with load histories of the frame to get the dangerous stress area. The fatigue life of the frame is calculated on the basis of Palmgren–Miner damage theory. It is turned out that the minimum life area of the frame is located at the frame joints of suspension, which matches the practice.

A surrogate model-based aerodynamic shape optimization method applied to the wind deflector of a tractor-trailer is presented in this paper. The aerodynamic drag coefficient of the tractor-trailer with and without the wind deflector subjected to crosswinds is analyzed. The numerical results show that the wind deflector can decrease drag coefficient. Four parameters are used to describe the wind deflector geometry: width, length, height, and angle. A 30-level design of experiments study using the optimal Latin hypercube method was conducted to analyze the sensitivity of the design variables and build a database to set up the surrogate model. The surrogate model was constructed based on the Kriging interpolation technique. The fitting precision of the surrogate model was examined using computational fluid dynamics and certified using a surrogate model simulation. Finally, a multi-island genetic algorithm was used to optimize the shape of the wind deflector based on the surrogate model. The tolerance between the results of the computational fluid dynamics simulation and the surrogate model was only 0.92% when using the optimal design variables, and the aerodynamic drag coefficient decreased by 4.65% compared to the drag coefficient of the tractor-trailer installed with the original wind deflector. The effect of the optimal shape of the wind deflector was validated by computational fluid dynamics and wind tunnel experiment.

For study the law of urban buildings, in particular, the buildings at both roads’ sides in crossroads impacting on the diffusion of automobile exhaust, using CFD, combined with meteorological wind，simulates a crossroads automobile exhaust diffusion processing during waiting 35s. The results are following: in poor circulation areas, CO volume fraction in the buildings near-Earth space is up to 1.0e-7 and more than 100 times average value of the entire study area, so buildings structural layout has great influence. After Analysis, propose that local meteorological wind direction and speed should be considered and different height gradient design should be selected in buildings structural layout, so that the exhaust spread rapidly and drift to the urban high altitude, in order to improve air quality.

Establishes 3d numerical simulation model of water side and air side for ribbon-tubular radiator, studies effect of air velocity on air side heat transfer capacity and drag characteristics by using CFD method, based on double side 3d simulation result, and then calculates the import and export water temperature of the high low temperature radiator group with procedure. The calculated water temperatures are coinciding with experimental data. Then analyzes the influence rule of different wave combinations to the radiator group performance by the method of simulation and procedure calculation, the result is reference theory for the structure optimization and matching of the radiator group.

Various return oil channels of a large self-dumping truck hydraulic tank don’t work synchronously brings the exit temperature fluctuations, traditional heat balance calculation can’t get some point temperature in tank, so it can’t be used to analyze temperature fluctuations. Selecting RNG k-εturbulent model and using CFD method，this paper analyzes flow field in the hydraulic tank of a certain large self-dumping truck at first, then according the principle of enhancing heat exchange, proposes two structure improved schemes, and contrasts the simulation result of two schemes, The results show that the two improved schemes reduce the tank exit temperature fluctuations and the high local temperature at different degrees, and the temperature fluctuations reduce range of the best scheme is 86.51% when the initial hydraulic oil temperature is 40°C.