scholarly journals Calculation of transonic flows around profiles with blunt and angled leading edges

2016 ◽  
Vol 38 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Hoang Thi Bich Ngoc ◽  
Nguyen Manh Hung
Keyword(s):  
Transonic Flow ◽  
Equations Of Motion ◽  
Physical Nature ◽  
Full Potential ◽  
Viscous Effects ◽  
Mixed Flow ◽  
Transonic Flows ◽  
Analysis Of Results ◽  
Supersonic Region ◽  
Leading Edges

Transonic flow is a mixed flow of subsonic and supersonic regions. Because of this mixture, the solution of transonic flow problems is obtained only when solving the differential equations of motion with special treatments for the transition from subsonic region to supersonic region and vice versa. We built codes solving the full potential equation and Euler equations by applying the finite difference method and finite volume method, and also associated with software Fluent to consider the viscous effects. The analysis of results calculated for cases of transonic flow over profiles with blunt and angled leading edges shows more clearly the physical nature of the gas - solid interaction at leading edges in the mixed flow and the optimal application of each profile in transonic flows.

scholarly journals Study of separation phenomenon in transonic flows produced by interaction between shock wave and boundary layer

2011 ◽  
Vol 33 (3) ◽  
pp. 170-181 ◽  
Author(s):  
Hoang Thi Bich Ngoc ◽  
Nguyen Manh Hung
Keyword(s):  
Boundary Layer ◽  
Shock Wave ◽  
Mach Number ◽  
Compressible Flows ◽  
Physical Nature ◽  
Boundary Layer Separation ◽  
Full Potential ◽  
Transonic Flows ◽  
Supersonic Region ◽  
Unique Factor

For compressible flows, the transonic state depends on the geometry, Mach number and the incidence. This effect can produce shock wave. Some studies showed that the interaction between shock wave and boundary layer concerns separation phenomenon. Studies in this report demonstrate conditions of separation in transonic flow and that it is not any interaction between shock wave and boundary layer which can cause boundary layer separation. The studies also show that maximum Mach number in the local supersonic region is not a unique factor influencing the separation, and the separation in transonic flows can occur at the incidence of 0\(^{\circ}\). For the calculation of viscous transonic flows, we use Fluent software with serious treatment of application operation based on the physical nature of phenomenon and the technique of numerical treatment. For the calculation of invicid transonic flows, we built a code solving the full potential equation with verification for accuracy. Results calculated from Fluent have been seriously compared with results of present program and published results in order to assure the accuracy of application operation in the domain of investigation. separation in transonic flows; shock wave and boundary layer

Computation of the Unsteady Transonic Flow in Harmonically Oscillating Turbine Cascades Taking Into Account Viscous Effects

1996 ◽  
Author(s):  
B. Grüber ◽  
V. Carstens
Keyword(s):  
Transonic Flow ◽  
Splitting Method ◽  
Euler Method ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Implicit Time ◽  
Test Case ◽  
Turbine Cascade ◽  
Viscous Effects ◽  
Unsteady Pressure

This paper presents the numerical results of a code for computing the unsteady transonic viscous flow in a two-dimensional cascade of harmonically oscillating blades. The flow field is calculated by a Navier-Stokes code, the basic features of which are the use of an upwind flux vector splitting scheme for the convective terms (Advection Upstream Splitting Method), an implicit time integration and the implementation of a mixing length turbulence model. For the present investigations two experimentally investigated test cases have been selected in which the blades had performed tuned harmonic bending vibrations. The results obtained by the Navier-Stokes code are compared with experimental data, as well as with the results of an Euler method. The first test case, which is a steam turbine cascade with entirely subsonic flow at nominal operating conditions, is the fourth standard configuration of the “Workshop on Aeroelasticity in Turbomachines”. Here the application of an Euler method already leads to acceptable results for unsteady pressure and damping coefficients and hence this cascade is very appropriate for a first validation of any Navier-Stokes code. The second test case is a highly-loaded gas turbine cascade operating in transonic flow at design and off-design conditions. This case is characterized by a normal shock appearing on the rear part of the blades’s suction surface, and is very sensitive to small changes in flow conditions. When comparing experimental and Euler results, differences are observed in the steady and unsteady pressure coefficients. The computation of this test case with the Navier-Stokes method improves to some extent the agreement between the experiment and numerical simulation.

FUNDAMENTAL CONCEPTS IN TRANSONIC FLOW PARADIGM OF BLACK HOLE ASTROPHYSICS

2011 ◽  
Vol 20 (10) ◽  
pp. 1723-1731 ◽  
Author(s):  
SANDIP K. CHAKRABARTI
Keyword(s):  
Black Hole ◽  
Numerical Simulations ◽  
Transonic Flow ◽  
Transonic Flows ◽  
Accretion Flow ◽  
New Concepts ◽  
The Subject

Exactly three decades ago, it was realized that an accretion flow onto a black hole should be transonic. Since then, the subject has matured considerably and several new and well established concepts and methodologies have replaced earlier ways of studying accretion and winds. Not surprisingly, with the advent of the faster computers as well as better space-based telescopes, the results of numerical simulations and the observations have also improved along with the theory. Today, it is more than satisfying that the results of theory and numerical simulations, even in the context of nonmagnetic flows, agree in details of the observations exceedingly well. I present here several new concepts and intricacies which one has to get familiar with when one talks about the behavior of the transonic flows, either in accretion or in the outflows.

A three-dimensional field-integral method for the calculation of transonic flow on complex configurations — theory and preliminary results

1988 ◽  
Vol 92 (916) ◽  
pp. 235-241 ◽  
Author(s):  
P. M. Sinclair
Keyword(s):  
Transonic Flow ◽  
Integral Method ◽  
Three Dimensional ◽  
Full Potential ◽  
Potential Equation ◽  
Direct Extension ◽  
Body Shapes ◽  
Dimensional Integral ◽  
Field Integral ◽  
Good Agreement

Summary A three-dimensional integral formulation for the solution of the full potential equation and the associated numerical algorithm, the field-integral method, are presented. The method is a direct extension of a two-dimensional method and in particular retains the simple grid generation requirements noted in that method. Results are presented for the flow over body shapes and a complex winglet configuration, and are compared with existing transonic methods and experiments with good agreement. The further work necessary to provide a fast, robust method for use in design is outlined.

scholarly journals Semi-Inverse Method of Computation in Inviscid Transonic Flows: Application to the Design of Turbomachines Blades Profiles

1981 ◽  
Author(s):  
H. Miton
Keyword(s):  
Transonic Flow ◽  
Inverse Method ◽  
Flow Problem ◽  
Order Approximation ◽  
Suction Side ◽  
Computational Technique ◽  
Input Flow ◽  
Flow Conditions ◽  
Transonic Flows ◽  
Channel Type

The present method is based on an original computational technique of quasi two-dimensional inviscid transonic flows but which takes into account the changes of entropy due to shocks. The present approach consists in a numerical 2nd order approximation of the real transonic flow problem (hyperbolic or elliptic) by an initial values problem of hyperbolic and parabolic nature respectively. Such a method applied to the flow field between two adjacent blades profiles allows starting from a prescribed distribution of velocity along blade pressure or suction side to determine the flow details inside this domain and the profile of the opposite blade wall corresponding to input flow conditions which however should be made to satisfy the periodicity conditions as at this stage the approach is of the channel type. Examples of computation for simple cases are shown which proves the validity of the method.

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