Sliding Mesh Technology Research Articles

Numerical Study of Aerodynamics of a Wing-in-Ground-Effect Craft

The flow around a wing-in-ground-effect craft flying at and over flat and wavy ground is simulated and investigated by using ANSYS FLUENT, employing the compressible Reynolds-averaged Navier–Stokes equations and the Spalart–Allmaras turbulence model. The sliding mesh technology is used to simulate the relative motion between the wing-in-ground-effect craft and wavy ground. The effects of the wavy ground, flight height, and angle of attack on the aerodynamic characteristics and flowfield are analyzed in detail. The aerodynamic forces are found to be periodic when the wing-in-ground-effect craft flies over wavy ground. The aerodynamic forces over both flat and wavy ground vary with flight height in the same pattern. As the flight height reduces, the lift, drag, and nose-down pitching moment all increase at both angles of attack ( and ); however, the lift-to-drag ratio increases for all flight heights at , while it first increases and then decreases at . Reduction in the flight height at eventually causes the attached flow to evolve into separated flow on the upper surface of the wing. Therefore, at higher angle of attack of , the lower the flight height is, the larger is the flow separation region; thus, the lift-to-drag ratio increases to the maximum at a certain flight height and then begins to decrease as the flight height decreases.

The Numerical Simulation of Unsteady Flow in a Mixed flow Pump Guide Vane

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluid's rotation is the same to impeller in the guide vane adhere.

Numerical simulation and performance prediction in multi-stage submersible centrifugal pump

In order to study the inner flow field of multi-stage submersible centrifugal pump, the model named QD3-60/4-1.1 was selected. Steady turbulence characteristics of impellers, diffusers and return channel were calculated by Fluent software, the SIMPLEC algorithm and RNG κ-ε turbulence model with sliding mesh technology. Then, the distributions of pressure, velocity and Turbulence kinetic energy was obtained and the distributions of velocity field of a channel were analysed. The results show that the static pressure in impeller is increasing with the increasing of radius. The circumferential component of relative velocity is in the opposite direction of impeller rotating. At the same radius, the component value of pressure surface is larger than suction surface. With the increasing of flow rate, absolute velocity and relative velocity flow angle are becoming small, in opposite of the relative velocity and absolute velocity flow angle. The high turbulent zone of impeller is located in the gap of impellers and diffusers. Flow similarity and structure similarity of the multi-stage submersible pump are confirmed.

Large Eddy Simulation of Unsteady Flow in a Mixed Flow Pump Guide Vane

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluids rotation is the same to impeller in the guide vane adhere.

Large Eddy Simulation of Unsteady Flow in a Mixed Flow Pump Guide Vane

In order to investigate the characteristics of unsteady flow in a mixed flow pump guide vane under the small flow conditions, several indicator points in a mixed flow pump guide vane was set, the three-dimensional unsteady turbulence numerical value of the mixed flow pump which is in the whole flow field will be calculated by means of the large eddy simulation (LES), sub-grid scale model and sliding mesh technology. The experimental results suggest that the large eddy simulation can estimate the positive slope characteristic of head & capacity curve. And the calculation results show that the pressure fluctuation coefficients of the middle section in guide vane inlet will decrease firstly and then increase. In guide vane outlet, the pressure fluctuation coefficients of section will be approximately axially symmetrical distribution. The pressure fluctuation minimum of section in guide vane inlet is above the middle location of the guide vane suction surface, and the pressure fluctuation minimum of section in which located the middle and outlet of guide vane. When it is under the small flow operating condition, the eddy scale of guide vane is larger, and the pressure fluctuation of the channel in guide vane being cyclical fluctuations obviously which leads to the area of eddy expanding to the whole channel from the suction side. The middle of the guide vane suction surface of the minimum amplitude pressure fluctuation to which the vortex core of eddy scale whose direction of fluids rotation is the same to impeller in the guide vane adhere.

Research on Aerodynamic Characteristics of Lateral Jet Control Technology

This paper takes N-S equation as the basic control equation, selects turbulence model, and adopts the sliding mesh technology to conduct numerical simulation for the interference of missile jet flow and inflow on the flow field in different flow conditions. The results indicate that: the lift coefficient, drag coefficient and pressure center coefficient of missile body change with the changes of flowMach number and attack angle. The lift coefficient increases with the increase of Mach number in subsonic speed, decreases with the increase of Mach number in supersonic speed, and reaches a maximum value with the increase of Mach number in transonic speed. The change rule of drag coefficient and pressure center coefficient is the same as that of lift coefficient. That is, they increase with the increase of Mach number in subsonic speed, and decrease with the increase of Mach number in supersonic speed.

Unsteady Aerodynamic Investigation of the Propeller-Wing Interaction for a Rocket Launched Unmanned Air Vehicle

The aerodynamic characteristics of propeller-wing interaction for the rocket launched UAV have been investigated numerically by means of sliding mesh technology. The corresponding forces and moments have been collected for axial wing placements ranging from 0.056 to 0.5 D and varied rotating speeds. The slipstream generated by the rotating propeller has little effects on the lift characteristics of the whole UAV. The drag can be seen to remain unchanged as the wing's location moves progressively closer to the propeller until 0.056 D away from the propeller, where a nearly 20% increase occurred sharply. The propeller position has a negligible effect on the overall thrust and torque of the propeller. The efficiency affected by the installation angle of the propeller blade has also been analyzed. Based on the pressure cloud and streamlines, the vortices generated by propeller, propeller-wing interaction, and wing tip have also been captured and analyzed.

Numerical simulation of the effect of solid-volume fraction on induction force of screw centrifugal pump

The solid-liquid two-phase unsteady flow in a screw centrifugal pump was simulated with unsteady Reynolds averaged Navier-Stokes equations and sliding mesh technology. The distribution of the pressure at volute outlet, radial force, axial force and total moment are presented in this paper. The effects of solid-phase volume fractions on the value and direction of the induction thrust are analyzed. Seven monitor points are arranged on the inner surface of volute along the impeller rotation. The characters of the induced force on the monitor points with different solid-phase volume fractions are investigated. The results indicated that different solid-volume fractions have litter effects on the trend and direction of pressure at volute, radial force, axial force and total moment during one period, but the value of induction forces increase with the increasing of solid-volume fraction; The pressure fluctuation on the monitor points has with different trends during one period, which depends on the direction of the monitor points and the rotor-stator interaction strength of impeller and volute. With the rotation of impeller, the values of pressure in the whole passage are further increased along the rotation direction with the role of impeller vane. Solid-phase volume fraction has few effects on change trend of induced thrust as radial force and axial force on the monitor points, but the values of pressure on the monitor points increase with the increasing of solid-volume fraction.

Numerical investigation of pressure fluctuation for a mixed flow pump impeller and vanes diffuser

In order to investigate the effect of rotor-stator interaction between impeller and vanes diffuser on the pressure fluctuation of a mixed flow pump, the pressure fluctuations at three representative locations under the design condition are obtained, unsteady flow feature is analyzed by RNG κ–ε turbulence model with sliding mesh technology. Experimental results show that there is the positive slope of head-flow performance curve under 0.6 and 0.85 design condition, which unsteady prediction is not seen based on Reynolds-averaged equation. The pressure fluctuation is analysed by the characteristics of amplitude and frequency, the amplitude of pressure fluctuation, which the maximum is in the rim of impeller outlet and the minimum is in the hub of impeller inlet, is gradually increasing along the hub to rim, the amplitude of monitoring points located the rim of impeller inlet and impeller and vanes diffuser is two times than the hub. The amplitude of pressure fluctuation, which the maximum is in the vanes diffuser outlet, is gradually increasing along impeller inlet to vanes diffuser outlet, while there is a low-frequency pressure fluctuation caused by unsteady flow in the vanes diffuser.

Numerical Simulation of Emergency Shutdown Process of Ring Gate in Hydraulic Turbine Runaway

A numerical model that considers the interaction between the ring gate and its neighboring components was used to simulate the emergency shutdown process of a ring gate in hydraulic turbine runaway. The three-dimensional, unsteady Navier–Stokes equations with renormalization group (RNG) k-ε turbulence models, multiphase flow models, dynamic mesh, and sliding mesh technology were applied to model the entire flow passage of the Francis hydraulic turbine, including the spiral case, stay vanes, ring gate, guide vanes, runner, and draft tube. We present a detailed analysis on the working conditions of the turbine during its runaway quitting process, the inside and outside surface pressure distributions of the ring gate, the pressure and velocity distributions of the spiral case, stay vanes, and guide vanes at different gate openings, and the loading condition of the ring gate during its closing process. The theoretical basis for improving the dynamic quality of the transient process and for hydraulic designing and optimization is provided by analyses.

NUMERICAL SIMULATION OF FLOW FIELD AND OPTIMIZATION OF STRUCTURE PARAMETERS OF VORTEX GRIT CHAMBER FOR SANDSTONE WASTEWATER TREATMENT

The problem of high concentration solid-liquid two-phase flow is difficult to overcome because the flow is complex in the vortex grit chamber. It leads to poor engineering design and operation. Eulerian - Eulerian solid-liquid two-phase flow model with the consideration of collision between particles is presented in this paper. The model is gained from the perspective of microscopic interaction between liquid and solid through the molecular kinetic theory and the computational fluid dynamics. Sliding mesh technology is used to simulate the vortex grit chamber in a hydropower sandstone wastewater treatment, Southwest China. The influences of the four factors including rotate speed, distance between the propeller and the base, number of propeller blades and angle of the propeller on the efficiency of the grit removal efficiency are studied. According to the single factor test, the optimal condition for the novel vortex grit chamber is that, the rotate speed of propeller is 105 rap/min, the distance between the propeller and the base is 592mm, the number of propeller blades is 4 and the angle of the propeller is 45?

Efficiency and Pressure Pulsation Analysis of a Double Suction Centrifugal Pump with Different Arrangement Impellers

Double suction centrifugal pumps are widely employed in large water supply projects. In the present study, a double suction centrifugal pump with the staggered arrangement impeller in a domestic water supply project has been mapping and modeling, and then the symmetrical arrangement impeller of a double suction centrifugal pump has been designed for comparison. The commercial code was used to investigate the pump efficiency and the time variation of pressure at the zone of volute tongue. This unsteady flow feature was investigated by the large eddy simulation (LES) method with the sliding mesh technology. The analysis indicated that the pump efficiency of the double suction centrifugal pump with staggered arrangement impeller is lower than that with the symmetrical one. The frequency of pressure pulsation at the volute tongue is consistent with the blade passing frequency. The staggered arrangement impeller can reduce the levels of pressure pulsation significantly.

The Characteristics Research of Tube Vortex Based on Large Eddy Simulation

Numerical simulation of three-dimensional transient turbulent flow in the whole flow passage of a Francis turbine were based upon the large eddy simulation(LES) technique on Smargorinsky model and sliding mesh technology. The steady flow data simulated with the standard k-εmodel was used as the initial conditions for the unsteady simulation. The results show that LES can do well transient turbulent flow simulation in a Francis turbine with complex geometry. The computational method provides some reference for exploring the mechanism of eddy formation in a complex turbulent of hydraulic machinery.

Numerical Simulation of Unsteady Pressure Field for Mammoth Electric Diving Pump

According to the feather of the many mine shafts extends to the deep, a new high lift head mammoth electric diving pump for drainage was developed. To study the unsteady characteristics that caused by interaction between the impeller and guide vanes, the sliding mesh technology and RNG k −ε Turbulence models was adopted to simulate the unsteady flow in the pump. The pressure distribution characteristics of the relevant section for the impeller, guide vane and return guide vane was obtained by calculation. The unsteady pressure fluctuation characteristic of each monitoring point was analyzed in the electric diving pump. The effective lift head by calculation fits the actual situation, which is greater than the measured lift head and has only 5% relative deviation.

Numerical Simulation and Particle Image Velocimeter Measurement for Unsteady Turbulent Flow in Double-channel Pump

To further study the unsteady flow mechanism in double-channel pump,simulations of turbulent flow in its whole flow channel are performed by using the flow computational software Fluent under different operating conditions,based on the sliding mesh technology and RNGkκ-e two-equation turbulence model.The calculation results are compared with the experimental data by particle image velocimeter(PIV).From the numerical and experimental research,it is found that,the calculated flow field conforms to the general flow rule in turbine machines,and its overall change tendency agrees well with PIV results;compared with the ordinary centrifugal-type impeller,its inlet flow status is quite different and outlet flow status changes little because of its special structure;in the impeller inlet,the fluid basically flows along the suction side,and the relative velocity is very small along the pressure side accompanied by serious separate flow and vortex;in the impeller outlet,the velocity on the pressure and suction side tends to be uniform,and jet flow phenomenon is not observed;as a result of interaction between the impeller and volute,static pressure distribution in one passage is different from another;in one flow channel,static pressure gradually increases with the radius increase,static pressure on pressure side is larger than that on suction side,and the biggest static pressure is near the tongue.This research will strengthen people's understanding of the unsteady turbulent flow pattern in double-channel pump,thus further improve the design method of double-channel pump,simultaneously might provide reference for internal flow research of other types of pumps.