Pressure Distribution Curve Research Articles

STUDY OF DRUG FORCE AND THE FLOW FIELD ON ROAD VEHICLES Khalid M. Sawoud

Improving road vehicles performance needs to deep understanding the science of aerodynamics, in order to control flow field by means of active and passive control techniques. The airflow behavior when passes over the road vehicles surfaces will be changes in patterns and resulting in different pressure regions. This pressure region causes drag force and thereby increases in fuel consumption of the road vehicles. This paper include experimental study to investigate the effect of road vehicles for three most common rear end configurations design such as (square, notch and fastback) on drag force, drag coefficient and pressure distribution. The experiments were carried out an open, low speed, and three dimensional wind-tunnel, on geometrical similarity to the prototype (Audi 80 1987) in scale down (1:18) wooden models for four different velocities (11.31, 13.86, 17.89 and 22.98) m/sec. The results obtained from the wind-tunnel investigations showed that the drag force increases with the increasing of free-stream velocities. The minimum drag coefficient can be achieved with fastback configuration, comparing with the other tested models and result in approximately 16% and 48% lower than that for notch and square back configurations, respectively. These results are demonstrated by the pressure distribution curves which provide a deep understanding of the flow behavior above the tested models.

Contact Pressure Distribution in Joints Formed by V-Band Clamps

V-band clamps offer an efficient clamping solution in diverse applications including process equipment, exhaust systems and air handling. This paper studies the distribution of interface contact pressure between the V-band and flange when the coupling is established. The determination of the contact area and pressure distribution in a joint is essential information, as it determines the integrity of the coupling. A three dimensional finite element model has been developed for this purpose. Contrary to the previous assumption in developing axisymmetric models, the 3D results showed that the contact pressure is non-uniform around the circumference of V-band with maximum contact pressure near the T-bolt area. This is in agreement with the theory in the literature. The presence and magnitude of friction has a noticeable influence on the form of the interface pressure distribution curve. It is also shown that the diameter of the band interacts with the effect of friction.

A Model of Adhesive Contact between a Spherical Tip and a Flat Surface

There have been increasing research interests in the measurement of the mechanical properties of nanoscale materials by pressing a spherical tip into surfaces of the tested materials. To acquire a better understanding of this process, a model of adhesive contact between a spherical tip and a flat surface is developed by employing the Hamaker hypotheses and molecular dynamics (MD) method. With this model, the deformation characteristics of the tested surface are illustrated by the key snapshots of the deformed surface and the corresponding curves of pressure distribution. The results indicate that the contact can be formed before the tip impresses into the surface. Moreover, the variation of the adhesive force with the distance is recorded during the approach and separation processes, and the adhesion hysteresis is demonstrated by the force-distance curve. Additionally, the stepwise increase of the contact radius with a decrease in the distance is revealed and investigated.

Numerical analysis of sheet cavitation on marine propellers, considering the effect of cross flow

The research performed in this paper was carried out to investigate the numerical analysis of the sheet cavitation on marine propeller. The method is boundary element method (BEM). Using the Green's theorem, the velocity potential is expressed as an integral equation on the surface of the propeller by hyperboloid-shaped elements. Employing the boundary conditions, the potential is determined via solving the resulting system of equations. For the case study, a DTMB4119 propeller is analyzed with and without cavitating conditions. The pressure distribution and hydrodynamic performance curves of the propellers as well as cavity thickness obtained by numerical method are calculated and compared by the experimental results. Specifically in this article cavitation changes are investigate in both the radial and chord direction. Thus, cross flow variation has been studied in the formation and growth of sheet cavitation. According to the data obtained it can be seen that there is a better agreement and less error between the numerical results gained from the present method and Fluent results than Hong Sun method. This confirms the accurate estimation of the detachment point and the cavity change in radial direction.

Transient numerical analysis of rotor–stator interaction in a Francis turbine

Pressure fluctuation due to rotor–stator interaction and occurrence of vortex rope in draft tube at partial load operation are obvious phenomena in Francis type reaction hydro turbines. These hydrodynamic effects are important issues and should be addressed during the design of hydraulic machines. A 3-dimensional transient state turbulent flow simulation in the entire flow passage of a 70 kW-Francis turbine having specific speed of 203.1 is conducted to investigate the rotor–stator interaction by adopting kω based SST turbulence model. The commercial 3D Navier–Stokes CFD solver Ansys-CFX is utilized to study the flow through this vertical shaft Francis turbine in its stationary and transient passages, at 100% optimum load and 72% of part load. The investigated turbine consists of a spiral casing with 16 guide vanes, 8 stay vanes, a runner with 13 blades and a draft tube. With a time step of 2° of a rotational period of the runner for 10 full rotations, the time dependent pressure and torque variations are monitored at the selected locations during the unsteady state calculation. A periodical behavior is observed for the pressure distribution in guide vanes, runner blades and torque in the runner blades. The pressure distribution curve in runner blades reveals the two dominating frequencies – the lower peaks due to runner speed and the upper peaks corresponding to the number of guide vanes interacting with the flow. The flow acceleration toward inside of the runner is depicted by the expanding wakes behind the stay vanes. Vortex rope is observed in draft tube, downstream the runner, at part-load operation.

Numerical experiment and analysis of the differential acoustic resonance spectroscopy for elastic property measurements

Differential acoustic resonance spectroscopy (DARS) was recently developed to estimate the elastic parameters of rock samples with a resonant frequency perturbation caused by a test sample at kilohertz frequency. In the derivation of the DARS theory, the wave inside the cavity is assumed to be a harmonic acoustic plane wave, which may be a source of measurement errors. A simulation program may help researchers to understand the mechanism of this device and to find out whether the assumption in the theory derivation is correct. In this paper, we develop a simulation program based on the elastic wave equation in cylindrical coordinates, and model the DARS system. The modeled power spectrum agrees well with that obtained by the laboratory measurement. An analysis of the wave field snapshots and the pressure distribution curves shows that the standing wave inside the cavity along its long axis is asymmetrical. This study also investigates the relationships between the resonant frequencies and the density, the compressibility and the P-wave and S-wave velocities of the samples. By numerical experiments, this paper finds that only the compressibility can be estimated with the resonant frequency, when the sample is located at the velocity node. But when the sample is located at other positions, the P-wave and S-wave velocities can alter the shape of the vibration curve, though they have no impact on the resonant power spectrum. This implies that it may be possible to estimate the P-wave and S-wave velocities by using the full waveform of the vibration curve.

The Influence of Micro-Texturing Dimple on the Bearing Capacity of the Elastohydrodynamic Lubrication Based on CFD-FSI Fluid-Solid Coupling

Based on the CFD-FSI fluid-solid coupled method, the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface on the condition of the medium velocity and medium load, low velocity and heavy load, high velocity and heavy load, low velocity and light load and high velocity and light load is respectively solved by numerical method in this paper. And obtain the oil film pressure distribution curve and the oil the film thickness distribution curve on the conditions of steady state, and analyze the influence of micro-texturing dimples on the bearing capacity of the equivalent elastohydrodynamic lubrication model. Analysis results show that: compared with the corresponding minimum film thickness on the conditions of smooth surface, the minimum film thickness of micro-texturing dimple surface on the conditions of the medium velocity and medium load, low velocity and light load is increased, which indicates the bearing capacity of the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface is increased; while the minimum film thickness of the rest conditions is decreased, which shows that the bearing capacity of the equivalent elastohydrodynamic lubrication model of the micro-texturing dimple surface is decreased. The study in this paper lays the foundation for the design and optimization of the micro-texturing dimple.

Experimental Research on Critical Force of Crushing and Sorting Coal Mine Gangue

First, The pressure test on two actual coal mine irregular and different particle sizes of coal and gangue, through the experimental data, using MATLAB software to give a graphic simulation and assumptions test of normal distribution, by the graphics and hypothetical test confirmed that coal and gangue had obvious demarcation, namely the critical force of crushing and storing coal gangue. In a coal mine as an example,and acquisiting more irregular and different particle sizes of coal and gangue were broken by static experiments and dynamic crushing experiment, using the experimental data obtained pressure distribution and pressure distribution curve equation,by equation to solve the crushing critical force FL of the size of 50-90mm coal and gangue,through mathematical and graphical analysis proved the rationality of FL,and providing a basic data for the future work.

Study on Crushing and Separation of Coal and Gangue

In this paper, the pressurization of irregular ores was first discussed so as to make an analysis on the causes for the great difference between measured result and actual ores, and then a preliminary pressure experiment was made on a certain quantity of coal and gangue samples extracted from Du'erping Coal Mine through electronic universal testing machine. Therefore, the selective crushing and separation of coal and gangue was preliminarily tested through the testing machine so as to obtain the selective crushing pressure distribution curves of coal and gangue, and then the curves were drawn based on its numerical distribution. The two curves drawn in this way were placed in the same coordinate, and the optimized control of the separation and selection of coal and gangue was made according to the probability values in the coordinate, so as to find a reasonable pressure boundary value and also prove that the separation and selection of coal and gangue are with certain feasibility.

Function Airfoil and its Pressure Distribution and Lift Coefficient Calculation

To study the impact of an airfoil shape on performance, a curve expression of airfoil shape was proposed, the analytical formula for the pressure distribution of flow around the airfoil was derived, and the pressure distribution view around airfoil with azimuth as the independent variable was put forward, which can clearly express the details of the pressure distribution curve on airfoil leading edge. Used both the pressure distribution integration method and Blasius theorem, the lift coefficient calculation formulas of ideal fluid flow around the airfoil were derived respectively, and the same results were obtained. Studies have shown that the shape of an airfoil can be expressed by a function, and various types of shapes can be easily obtained by adjusting the constant value in the expression; The pressure distribution and lift coefficient can be calculated by analytical method; For function airfoil, lift coefficient formula could be derived by two methods, and could be verified with each other. The one-to-one relationship exists between the constant values in the airfoil function, airfoil shapes and airfoil performances, and the relationship expression was given in this paper.

Study on Influence of Back Angle on Human Body Pressure Distribution

Through the study of the seat size parameter change on the body pressure distribution effect, the powerful references to comfort design of office chair were explored. By using Canadian XSENSOR X3 PRO V6 test system, human body pressure distribution and subjective comfort evaluation in different back angle of 6 objects were tested. The data were processed by statistical analysis software SPSS 16. Then the change of maximum pressure, average pressure, contact area of seat surface and backrest, as well as the vertical pressure distribution curve with the back angle were obtained. Finally the comfort indicators of daily office chair were determined based on body pressure distribution, and the most comfortable back angle of office chair were also solved. Thereby it can provide reference for those who want to design comfortable daily office chair.

Research on Influence of Parameters Variation on the Fixed Orifice Performance of the Servo-Valve

In this paper, The finite element analysis software is applied to compute the flow field in the fixed orifice with different structural parameter combinations, the pressure distribution curve, the velocity distribution curve, flow rate characteristic, power loss are obtained. By analyzing simulation results, the influence of the orifice parameters on the performance of the orifice is clear. The research is important for the design and optimization of the fixed throttle orifice of the nozzle-flapper valve.

Experimental and Theoretical Study for Pizometric

In this work an experimental and theoretical study was done to test the effect of upstream, intermediate and down stream sheet piles inclination ,then the optimum case of the uplift pressure reduction was found .The study consisted 12 separated case of these inclined sheet piles with changing the direction of this inclination .Two angles of the inclination were tested 37,67 for each sheet pile .Many of uplift pressure distribution curves under the structure were plotted .Many conclusions for each sheet pile were found also.

327 高次曲線分布の接地圧による異方性ブラシモデルとグリップマージン推定(車両駆動系の解析と制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

327 高次曲線分布の接地圧による異方性ブラシモデルとグリップマージン推定(車両駆動系の解析と制御,OS-16 運動と振動の制御,総合テーマ「伝統を,未来へ!」)

Analyzing the Cold Rolling of Aluminium Using a New Software (Matroll)

A good analyze of aluminum cold rolling is almost impossible without a good knowledge of rolling parameters. Besides, to optimize and stabilize the process, the interactions among various factors during rolling should be known. Thus, controlling the parameters affecting this process is of significant importance in order to have a product with high quality and efficiency. In the present work, using a new software (MATROLL), attempts have been made to analyze the cold rolling process of aluminum. Eight cold rolling passes were carried out on a real industrial mill. It was found that when the coefficient of friction (COF) drops to below about 0.035, the rolling is going to be unstable. This value of is named here Optimum COF when below it the process is metastable. including the coefficient of friction (COF) and pressure distribution curves so-called friction hills. The results (outputs) are in good agreements with the findings of other researchers so that the reliable analyses can be established.

FLOW CHARACTERISTICS OF ELLIPTICAL ORIFICE PLATES

ABSTRACT This paper presents the results of the experimental investigation concerning the clear water flow through elliptical orifice plates in a circular pipe. Experiments were conducted in a pipe line having diameter of 38.1 mm and using elliptical orifice plates with orifice area to pipe area a/A = 0.20, 0.33, 0.50, 0.66 and 0.84. For a comparative study, five circular orifice plates with same a/A ratios were also tested simultaneously. The data collected in the present study alongwith the data collected from literature have been analysed to study the position of vena contracta, and variation of discharge coefficient Cd with relevant flow and geometric parameters. The dimensionless pressure distribution curves were analysed to locate the position of vena contracta with area ratio. The position of vena contracta is a function of area ratio. As area ratio increases, the location of the vena contracta shifts towards the orifice plate. Similarly, the position of vena contracta Lv/D is a function of ellipticity ‘e’ which is defined as the ratio of minor axis to major axis of the ellipse i.e. 2bo/2ao and the displacement angle θ. The angle θ is the angle between the X-axis and major axis (2ao) of the ellipse. As ellipticity increases the position of vena contracta decreases. Also as displacement increases, the position of vena contracta decreases. Further, it has been found that for low values of orifice Reynolds number Ro, Cd depends on both a/A ratio and Ro. At higher Ro values (Ro≥3×104), Cd depends only of a/A ratio. For the same area ratio a/A, the elliptical (Horizontal) orifice plate has smaller values of coefficient of discharge at higher Ro as compared to circular orifice plates. For higher Ro values, the relationship between limiting values of discharge coefficient Cdl and a/A for elliptical orifice plates is given by the equation Cdl = 0.596-0.324(a/A)+1.01(a/A)2 Also at higher Ro values, the relationship between Cdl and a/A for different shapes of orifice plates is given by Cdl = 0.639—0.288(a/A)+0.817(a/A)2 The limiting Cd values i.e. Cdl increases as ellipticity increases for all a/A ratio. However, there is no significant effect on Cdl with displacement angle θ.

Analytical solution for determining the critical condition of saltwater upconing in a leaky artesian aquifer

Saltwater upconing that occurs in an aquifer overlain by a leaky confining unit is described by an analytical model that assumes the existence of a sharp interface between the freshwater and saltwater and the occurrence of a critical rise in the interface, above which only an unstable cone can exist. At the critical rise, the pressure on the freshwater side of the interface is equal to the pressure on the saltwater side of the interface. Also, the curve for pressure versus depth on the freshwater side of the interface is tangent to the curve for pressure versus depth on the saltwater side of the interface at the critical condition, and thus the slopes of the freshwater and saltwater pressure distribution curves are equal. These two conditions, equality of pressures and equality of pressure gradients, are used to derive two equations that can be solved simultaneously for the critical interface rise and the associated critical pumping rate. Instead of assuming a fixed value for the critical rise of the interface, its location is calculated using an analytical equation expressed in terms of aquifer and confining unit properties and well geometry. The associated critical pumping rate is calculated as a function of aquifer and confining unit properties, well geometry, and the critical interface rise ratio. For field conditions, the critical rise of the interface and critical pumping rate can be calculated analytically or graphically. In an example calculation, the critical interface rise ratio, which is the ratio of the critical interface rise divided by the distance from the original location of the interface to the bottom of the pumped well, is calculated to be 0.710 and the critical pumping rate is calculated to be 3.72×10 4 m 3/day.

Modelling of infiltration of molten metal in fibrous preform by centrifugal force

Infiltration kinetics of molten metal in fibrous preforms by centrifugal force is discussed theoretically. The relationship between the location of infiltration front and time is introduced for three major types of centrifugal casting processes. By the relationship, pressure distribution curves in the preform are also obtained. Some calculated examples are shown for the infiltration of molten aluminum into an alumina short fiber preform. If the speed of revolution is slightly higher than the minimum value determined by threshold pressure, infiltration is continuous. Since the second derivative of the pressure distribution curves in the infiltrated region is always positive and proportional to angular velocity in the centrifugal force field, the pressure curves are convex toward low pressure. When the surface pressure of the preform is low enough or the speed of revolution is high, the region having lower pressure than the threshold pressure appears in the infiltrated region. These results are compared with experimental data from references and by the authors.

Drag Reduction in Flow Past a Circular Cylinder in Water/Fine Solid Particle Suspension.

Experiments were performed on the flow past a circular cylinder in silica dioxide suspensions with Cw=0.5∼1.0wt% and in carbon black suspensions with Cw=0.3∼1.0wt%. Two cylinders with diameters between 10mm and 20mm located in a horizontal duct were tested in terms of the pressure distribution. It was shown that the separation point shifts downstream although the Strouhal number is almost the same as that of tap water. Consquently, from the result of an integration along the pressure distribution curve it is clarified that the drag reduction phenomenon in water/fine solid particle suspension is caused by the shift of the separation point in a certain Reynolds number range.

Mathematical modeling of freshwater-saltwater systems: A response to discussion of “A density-dependent flow and transport analysis of the effects of groundwater development in a freshwater lens of limited areal extent: The Geneva area (Florida, U.S.A.) case study, by Panday et al. (1993)”, by Motz (1995 in this issue)

Saltwater upconing that occurs in an aquifer overlain by a leaky confining unit is described by an analytical model that assumes the existence of a sharp interface between the freshwater and saltwater and the occurrence of a critical rise in the interface, above which only an unstable cone can exist. At the critical rise, the pressure on the freshwater side of the interface is equal to the pressure on the saltwater side of the interface. Also, the curve for pressure versus depth on the freshwater side of the interface is tangent to the curve for pressure versus depth on the saltwater side of the interface at the critical condition, and thus the slopes of the freshwater and saltwater pressure distribution curves are equal. These two conditions, equality of pressures and equality of pressure gradients, are used to derive two equations that can be solved simultaneously for the critical interface rise and the associated critical pumping rate. Instead of assuming a fixed value for the critical rise of the interface, its location is calculated using an analytical equation expressed in terms of aquifer and confining unit properties and well geometry. The associated critical pumping rate is calculated as a function of aquifer and confining unit properties, well geometry, and the critical interface rise ratio. For field conditions, the critical rise of the interface and critical pumping rate can be calculated analytically or graphically. In an example calculation, the critical interface rise ratio, which is the ratio of the critical interface rise divided by the distance from the original location of the interface to the bottom of the pumped well, is calculated to be 0.710 and the critical pumping rate is calculated to be 3.72×104 m3/day.