scholarly journals Determination of air and hydrofoil pressure coefficient by laser doppler anemometry

2010 ◽  
Vol 37 (1) ◽  
pp. 17-35
Author(s):  
Slavica Ristic ◽  
Mirjana Puharic ◽  
Marina Kutin ◽  
Dusan Matic
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Laser Doppler Anemometry ◽  
Pressure Coefficient ◽  
Laser Doppler ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Advantages And Disadvantages ◽  
Axial Pump

Some results of experiments performed in water cavitation tunnel are presented. Pressure coefficient (Cp) was experimentally determined by Laser Doppler Anemometry (LDA) measurements. Two models were tested: model of airplane G4 (Super Galeb) and hydrofoil of high speed axial pump. These models are not prepared for conventional pressure measurements, so that LDA is applied for Cp determination. Numerical results were obtained using a code for average Navier-Stokes equations solutions. Comparisons between computational and experimental results prove the effectiveness of the LDA. The advantages and disadvantages of LDA application are discussed. Flow visualization was made by air bubbles.

Aerodynamic Simulation of the Air Flow beneath the High Speed Train

2012 ◽  
Vol 253-255 ◽  
pp. 2035-2040
Author(s):  
Ye Bo Liu ◽  
Zhi Ming Liu
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Air Flow ◽  
Pressure Coefficient ◽  
Three Dimensional ◽  
Navier Stokes ◽  
High Speed Train ◽  
Navier Stokes Equations ◽  
Pressure Distributions ◽  
High Speed Trains

Numerical simulations were carried out to investigate the air flow and pressure distributions beneath high speed trains, based on the three-dimensional Reynolds-averaged Navier-Stokes equations with the SST k-ω two-equation turbulence model. The simulation scenarios were of the high speed train, the CRH2, running in the open air at four different speeds: 200km/h, 250km/h, 300km/h and 350km/h. The results show that, the highest area of pressure is located at the front underbody part of the train whist the pressure for rest of the train is relatively small. Increasing speed does not visibly increase the pressure coefficient, indicating that the pressure increases with the square of the operational speed.

scholarly journals Simulation of Poiseuille flow

2021 ◽  
pp. 1-29
Author(s):  
Georgy Sergeevich Chashchin
Keyword(s):  
Lattice Boltzmann Method ◽  
Poiseuille Flow ◽  
Lattice Boltzmann ◽  
High Speed ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Cartesian Grids ◽  
Navier Stokes Equations ◽  
Advantages And Disadvantages ◽  
Boltzmann Method

In this article, plane and space Poiseuille flow was simulate of the lattice Boltzmann method. Because Poiseuille solution is one of the simplest solutions Navier-Stokes equations, it is well for exploring opportunities of lattice Boltzmann method. Simulation flows in plane rectangular and ellipsoidal cylindrical pipes assist to detect advantages and disadvantages of original and Dellar’s regularized lattice Boltzmann algorithm on standard lattices with different started and boundaries conditions. LBM’s main excellence is high speed of calculation, but it’s manifest imperfection is using Cartesian grids and not evident generalization on another grid’s types.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

scholarly journals Flow Pressure Behavior Downstream of Ski Jumps

Fluids ◽  
2020 ◽  
Vol 5 (4) ◽  
pp. 168 ◽  
Author(s):  
Agostino Lauria ◽  
Giancarlo Alfonsi ◽  
Ali Tafarojnoruz
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Dynamic Pressure ◽  
Pressure Head ◽  
Navier Stokes ◽  
Maximum Pressure ◽  
Navier Stokes Equations ◽  
Free Jet ◽  
Jet Characteristics ◽  
The Impact

Ski jump spillways are frequently implemented to dissipate energy from high-speed flows. The general feature of this structure is to transform the spillway flow into a free jet up to a location where the impact of the jet creates a plunge pool, representing an area for potential erosion phenomena. In the present investigation, several tests with different ski jump bucket angles are executed numerically by means of the OpenFOAM® digital library, taking advantage of the Reynolds-averaged Navier–Stokes equations (RANS) approach. The results are compared to those obtained experimentally by other authors as related to the jet length and shape, obtaining physical insights into the jet characteristics. Particular attention is given to the maximum pressure head at the tailwater. Simple equations are proposed to predict the maximum dynamic pressure head acting on the tailwater, as dependent upon the Froude number, and the maximum pressure head on the bucket. Results of this study provide useful suggestions for the design of ski jump spillways in dam construction.

scholarly journals New variational principles for locating periodic orbits of differential equations

2011 ◽  
Vol 369 (1944) ◽  
pp. 2211-2218 ◽  
Author(s):  
Bruce M. Boghosian ◽  
Luis M. Fazendeiro ◽  
Jonas Lätt ◽  
Hui Tang ◽  
Peter V. Coveney
Keyword(s):  
Periodic Orbits ◽  
Variational Principles ◽  
Stokes Equations ◽  
Iterative Algorithms ◽  
Navier Stokes ◽  
Unstable Periodic Orbits ◽  
Navier Stokes Equations ◽  
New Methods ◽  
Discrete Representations

We present new methods for the determination of periodic orbits of general dynamical systems. Iterative algorithms for finding solutions by these methods, for both the exact continuum case, and for approximate discrete representations suitable for numerical implementation, are discussed. Finally, we describe our approach to the computation of unstable periodic orbits of the driven Navier–Stokes equations, simulated using the lattice Boltzmann equation.

Numerical simulation of the stalled flow within a vaned centrifugal pump

2004 ◽  
Vol 218 (4) ◽  
pp. 425-435 ◽  
Author(s):  
K M Guleren ◽  
A Pinarbasi
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
High Speed ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Navier Stokes Equations ◽  
Low Pass

The main goal of the present work is to analyse the numerical simulation of a centrifugal pump by solving Navier-Stokes equations, coupled with the ‘standard k-∊’ turbulence model. The pump consists of an impeller having five curved blades with nine diffuser vanes. The shaft rotates at 890r/min. Flow characteristics are assumed to be stalled in the appropriate region of flowrate levels of 1.31-2.861/s. Numerical analysis techniques are performed on a commercial FLUENT package program assuming steady, incompressible flow conditions with decreasing flowrate. Under stall conditions the flow in the diffuser passage alternates between outward jetting when the low-pass-filtered pressure is high to a reverse flow when the filtered pressure is low. Being below design conditions, there is a consistent high-speed leakage flow in the gap between the impeller and the diffuser from the exit side of the diffuser to the beginning of the volute. Separation of this leakage flow from the diffuser vane causes the onset of stall. As the flowrate decreases both the magnitude of the leakage within the vaneless part of the pump and reverse flow within a stalled diffuser passage increase. As this occurs, the stall-cell size extends from one to two diffuser passages. Comparisons are made with experimental data and show good agreement.

Simulation of the subsonic flow in a high-speed centrifugal compressor impeller by the pressure-based method

1998 ◽  
Vol 212 (4) ◽  
pp. 269-287 ◽  
Author(s):  
Y Wang ◽  
S Komori
Keyword(s):  
High Speed ◽  
Compressible Flows ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Navier Stokes Equations ◽  
Compressor Impeller ◽  
Collocated Grid

A pressure-based finite volume procedure developed previously for incompressible flows is extended to predict the three-dimensional compressible flow within a centrifugal impeller. In this procedure, the general curvilinear coordinate system is used and the collocated grid arrangement is adopted. Mass-averaging is used to close the instantaneous Navier-Stokes equations. The covariant velocity components are used as the main variables for the momentum equations, making the pressure-velocity coupling easier. The procedure is successfully applied to predict various compressible flows from subsonic to supersonic. With the aid of the k-ɛ turbulence model, the flow details within a centrifugal impeller are obtained using the present procedure. Predicted distributions of the meridional velocity and the static pressure are reasonable. Calculated radial velocities and flow angles are favourably compared with the measurements at the exit of the impeller.

Study of Laminar, Unsteady Piston-Cylinder Flows

1993 ◽  
Vol 115 (4) ◽  
pp. 687-693 ◽  
Author(s):  
H. Stro¨ll ◽  
F. Durst ◽  
M. Peric´ ◽  
J. C. F. Pereira ◽  
G. Scheuerer
Keyword(s):  
Stokes Equations ◽  
Axisymmetric Flow ◽  
Simple Algorithm ◽  
Laser Doppler ◽  
Sudden Expansion ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Measuring Point ◽  
Curvature Effects ◽  
Piston Cylinder

The present paper concerns numerical investigation of a piston-driven, axisymmetric flow in a pipe assembly containing a sudden expansion. The piston closes the larger of the two pipes. The impulsively starting intake flow is the topic of this investigation. Results of numerical calculations and laser-Doppler measurements are presented to provide an insight into the features of the flow. The calculation procedure employed in this study is based on a finite-volume method with staggered grids and SIMPLE-algorithm for pressure-velocity coupling (Patankar and Spalding, 1972). The convection and diffusion fluxes in the Navier-Stokes equations are discretized with first order upwind and second order central differences, respectively. A fully implicit Euler scheme is used to discretize the temporal derivatives. The Navier-Stokes equations were suitably transformed to allow prediction of the flow within the inlet pipe (fixed grid) and cylinder region (moving grid) simultaneously (once-through procedure). Laser-Doppler measurements of both axial and radial velocity components were performed. Refractive index matching was used to eliminate the wall curvature effects. For each measuring point 20 cycles were measured, showing high repetition rates. Comparison of measured and predicted velocity profiles shows good agreement.

Computations of the Compressible Multiphase Flow Over the Cavitating High-Speed Torpedo

2003 ◽  
Vol 125 (3) ◽  
pp. 459-468 ◽  
Author(s):  
F. M. Owis ◽  
Ali H. Nayfeh
Keyword(s):  
High Speed ◽  
Multiphase Flows ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Multiphase System ◽  
System Of Equations ◽  
Cavitating Flows ◽  
Navier Stokes Equations ◽  
Compressible Multiphase Flow ◽  
Speed Flow

For high-speed cavitating flows, compressibility becomes significant in the liquid phase as well as in the vapor phase. In addition, the compressible energy equation is required for studying the effects of the propulsive jet on the cavity. Therefore, a numerical method is developed to compute cavitating flows over high-speed torpedoes using the full unsteady compressible Navier-Stokes equations. The multiphase system of equations is preconditioned for low-speed flow computations. Using the mass fraction form, we derive an eigensystem for both the conditioned and the nonconditioned system of equations. This eigensystem provides stability for the numerical discretization of the convective flux and increases the convergence rate. This method can be used to compute single as well as multiphase flows. The governing equations are discretized on a structured grid using an upwind flux difference scheme with flux limits. Single as well as multiphase flows are computed over a cavitating torpedo. The results indicate that the preconditioned system of equations converges rapidly to the required solution at very low speeds. The theoretical results are in good agreement with the measurements.

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