Assessing Viscous Body Forces for Unsteady Calculations

2003 ◽  
Vol 125 (3) ◽  
pp. 425-432 ◽  
Author(s):  
L. Xu
Keyword(s):  
Drag Coefficient ◽  
Body Force ◽  
Three Dimensional ◽  
Viscous Force ◽  
Local Source ◽  
Source Terms ◽  
Viscous Effects ◽  
Computational Mesh ◽  
Blade Row ◽  
Computational Resources

A strategy has been developed to model the three-dimensional unsteady flows through turbomachines subject to nonaxisymmetric flow/geometrical conditions such as low order distortions with relatively long length-scale unsteadiness, by modeling the viscous effects as local source terms for a coarse computational mesh, but not calculating them directly. In general full annulus multi-row calculations are required for such flows, but currently the computational resources are devoted to resolving detailed viscous flow very close to the walls, which in some cases is not the center of concern. By avoiding resolving detailed viscous effects the model can accelerate the calculation by at least two orders of magnitude. The method has been illustrated to be able to resolve disturbances down to the blade passing frequency and give good estimates of overall unsteady blade forces due to blade row interactions. Obviously, the correct modeling of the viscous body force as source terms in the governing equations is the key for accuracy of such calculations. Different ways of constructing/approximating the viscous body force term are discussed and their adequacy in unsteady flow calculations is assessed. It is found that in general the viscous force is relatively small compared to the total blade force, even smaller the unsteady fluctuation of the viscous force and a simple drag coefficient model is quite adequate to model both time mean and dynamic viscous effects. However, for the cases when separations are present variations in the drag coefficient may become large and more detailed modeling may be required.

Assessing Viscous Body Forces for Unsteady Calculations

2002 ◽  
Author(s):  
L. Xu
Keyword(s):  
Drag Coefficient ◽  
Body Force ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Viscous Force ◽  
Local Source ◽  
Source Terms ◽  
Viscous Effects ◽  
Computational Mesh ◽  
Computational Resources

A strategy has been developed to model the three dimensional unsteady flows through turbomachines subject to non-axisymmetric flow/geometrical conditions such as low order distortions with relatively long length scale unsteadiness, by modelling the viscous effects as local source terms for a coarse computational mesh but not calculating them directly. In general full annulus multirow calculations are required for such flows but currently the computational resources are devoted to resolving detailed viscous flow very close to the walls, which in some cases is not the centre of concern. By avoiding resolving detailed viscous effects the model can accelerate the calculation by at least two orders of magnitude. The method has been illustrated to be able to resolve disturbances down to the blade passing frequency and give good estimates of overall unsteady blade forces due to blade row interactions. Obviously the correct modelling of the viscous body force as source terms in the governing equations is the key for accuracy of such calculations. Different ways of constructing/approximating the viscous body force term are discussed and their adequacy in unsteady flow calculations is assessed. It is found that in general the viscous force is relatively small compared to the total blade force, even smaller the unsteady fluctuation of the viscous force and a simple drag coefficient model is quite adequate to model both time mean and dynamic viscous effects. Whilst for the cases when separations are present variations in the drag coefficient may become large and more detailed modelling may be required.

1997 Best Paper Award—Education Committee: A Three-Dimensional Turbine Engine Analysis Compressor Code (TEACC) for Steady-State Inlet Distortion

1998 ◽  
Vol 120 (3) ◽  
pp. 422-430 ◽  
Author(s):  
A. Hale ◽  
W. O’Brien
Keyword(s):  
Three Dimensional ◽  
Simulation Tool ◽  
Source Terms ◽  
Turbine Engine ◽  
Streamline Curvature ◽  
Inlet Distortion ◽  
Blade Row ◽  
Practical Design ◽  
Distorted Region ◽  
Computationally Intensive

The direct approach of modeling the flow between all blade passages for each blade row in the compressor is too computationally intensive for practical design and analysis investigations with inlet distortion. Therefore a new simulation tool called the Turbine Engine Analysis Compressor Code (TEACC) has been developed. TEACC solves the compressible, time-dependent, three-dimensional Euler equations modified to include turbomachinery source terms, which represent the effect of the blades. The source terms are calculated for each blade row by the application of a streamline curvature code. TEACC was validated against experimental data from the transonic NASA rotor, Rotor 1B, for a clean inlet and for an inlet distortion produced by a 90-deg, one-per-revolution distortion screen. TEACC revealed that strong swirl produced by the rotor caused the compressor to increase in loading in the direction of rotor rotation through the distorted region and decrease in loading circumferentially away from the distorted region.

A Transport Model for the Deterministic Stresses Associated With Turbomachinery Blade Row Interactions

2000 ◽  
Vol 122 (4) ◽  
pp. 593-603 ◽  
Author(s):  
Allan G. van de Wall ◽  
Jaikrishnan R. Kadambi ◽  
John J. Adamczyk
Keyword(s):  
Turbine Blade ◽  
Transport Model ◽  
Three Dimensional ◽  
Tip Clearance ◽  
Two Dimensional ◽  
Mean Flow ◽  
Viscous Effects ◽  
Vortical Structures ◽  
Blade Row ◽  
The Mean

The unsteady process resulting from the interaction of upstream vortical structures with a downstream blade row in turbomachines can have a significant impact on the machine efficiency. The upstream vortical structures or disturbances are transported by the mean flow of the downstream blade row, redistributing the time-average unsteady kinetic energy (K) associated with the incoming disturbance. A transport model was developed to take this process into account in the computation of time-averaged multistage turbomachinery flows. The model was applied to compressor and turbine geometry. For compressors, the K associated with upstream two-dimensional wakes and three-dimensional tip clearance flows is reduced as a result of their interaction with a downstream blade row. This reduction results from inviscid effects as well as viscous effects and reduces the loss associated with the upstream disturbance. Any disturbance passing through a compressor blade row results in a smaller loss than if the disturbance was mixed-out prior to entering the blade row. For turbines, the K associated with upstream two-dimensional wakes and three-dimensional tip clearance flows are significantly amplified by inviscid effects as a result of the interaction with a downstream turbine blade row. Viscous effects act to reduce the amplification of the K by inviscid effects but result in a substantial loss. Two-dimensional wakes and three-dimensional tip clearance flows passing through a turbine blade row result in a larger loss than if these disturbances were mixed-out prior to entering the blade row. [S0889-504X(00)01804-3]

Research on the Improved Body-Force Method Based on Viscous Flow

2019 ◽  
Author(s):  
Zhiheng Li ◽  
Jiawei Yu ◽  
Dakui Feng ◽  
Kaijun Jiang ◽  
Yujie Zhou
Keyword(s):  
Drag Coefficient ◽  
Viscous Flow ◽  
Body Force ◽  
Lift Coefficient ◽  
Open Water ◽  
Viscous Effects ◽  
Thrust Coefficient ◽  
Force Method ◽  
Water Characteristics ◽  
Body Force Method

Abstract The virtual propeller model can achieve the rapid numerical prediction of the ship self-propulsion performance through viscous flow, which used the improved body-force method. The two-dimensional lift coefficient CL and the drag coefficient CD are very important parameters in this method, which are generally obtained by the potential flow methods and cannot incorporate viscous effects. This study will perform a fully nonlinear unsteady RANS (Reynolds Average Navier-Stokes) simulation to get the KP505 open-water characteristics and then divide its blade into several parts to get the lift coefficient CL and the drag coefficient CD on each one. Then fitting by multivariate regression method, the relationship between CL, CD and propeller parameters is obtained. The Unsteady Blade Element Theory (UBET) is coupled with RANS in house CFD code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) to calculate the flow around the propeller. RANS equations are solved by the finite difference method and PISO arithmetic. have been made using structured grid with overset technology. The results show that comparing with the EFD data, the maximum differences of the result of the improved body-force method are 4.32% and 2.7% for the thrust coefficient and the torque coefficient respectively near the propeller operating point.

scholarly journals A Three-Dimensional Turbine Engine Analysis Compressor Code (TEACC) for Steady-State Inlet Distortion

1997 ◽  
Author(s):  
Alan Hale ◽  
Walter O’Brien
Keyword(s):  
Three Dimensional ◽  
Simulation Tool ◽  
Source Terms ◽  
Turbine Engine ◽  
Streamline Curvature ◽  
Inlet Distortion ◽  
Blade Row ◽  
Practical Design ◽  
Distorted Region ◽  
Computationally Intensive

The direct approach of modeling the flow between all blade passages for each blade row in the compressor is too computationally intensive for practical design and analysis investigations with inlet distortion. Therefore a new simulation tool called the Turbine Engine Analysis Compressor Code (TEACC) has been developed. TEACC solves the compressible, time-dependent, 3D Euler equations modified to include turbomachinery source terms which represent the effect of the blades. The source terms are calculated for each blade row by the application of a streamline curvature code. TEACC was validated against experimental data from the transonic NASA rotor, Rotor 1B, for a clean inlet and for an inlet distortion produced by a 90-deg, one-per-revolution distortion screen. TEACC revealed that strong swirl produced by the rotor caused the compressor to increase in loading in the direction of rotor rotation through the distorted region and decrease in loading circumferentially away from the distorted region.

scholarly journals The Use of a Distributed Body Force to Simulate Viscous Effects in 3D Flow Calculations

1986 ◽  
Author(s):  
J. D. Denton
Keyword(s):  
Simple Model ◽  
Viscous Flow ◽  
Body Force ◽  
Computational Cost ◽  
Three Dimensional ◽  
Secondary Flows ◽  
The Other ◽  
Simple Extension ◽  
Viscous Effects ◽  
3D Flow

Three dimensional viscous flow calculations methods for turbomachinery are starting to become available but are not yet sufficiently well developed to be used for design purposes. Three dimensional inviscid calculations on the other hand are now well developed and are widely used for design purposes. This paper describes a method intermediate between fully viscous methods and inviscid methods. The viscous effects are approximated by a very simple model which can be tuned empirically to get the correct overall level of loss and which reproduces many of the details of real viscous flow, such as boundary layers and secondary flows. The method is a simple extension to a widely used inviscid method and enables viscous effects to be simulated with little extra computational cost compared to a 3D inviscid calculation.

Development of body force model for steady inlet distortions in high-speed multistage compressor

2016 ◽  
Vol 231 (9) ◽  
pp. 1650-1659 ◽  
Author(s):  
Jin Guo ◽  
Jun Hu
Keyword(s):  
Performance Analysis ◽  
Body Force ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
The Body ◽  
Force Model ◽  
Source Terms ◽  
Analysis Model ◽  
Multistage Compressor ◽  
The Impact

This study aims at establishing a three-dimensional numerical model, compressor aerodynamic performance analysis model, to simulate the impact of complicated distorted flow on multistage axial flow compressor based on the body force model. The model solves the compressible three-dimensional Euler equations, which are modified to include source terms representing the effect of the blade rows. In this study, the association between blade source terms and entry Mach number together with attack angle could be established with the deviation angle model and loss model. In this paper, compressor aerodynamic performance analysis model is used to evaluate the effect of inlet circumferential total pressure distortion and swirl distortion on a five-stage high-pressure compressor. Calculated operating maps for compressor agree well with the experimental results. Meanwhile, the traveling process of inlet distortions in the multistage compressor is correctly revealed. The wide application prospect of the model can be seen in the area of inlet distortion problems.

scholarly journals A Three-Dimensional Unsteady CFD Model of Compressor Stability

2006 ◽  
Author(s):  
R. V. Chima
Keyword(s):  
Input Data ◽  
Body Force ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Rotating Stall ◽  
The Body ◽  
Navier Stokes ◽  
Blade Row ◽  
Operating Points

A three-dimensional unsteady CFD code called CSTALL has been developed and used to investigate compressor stability. The code solved the Euler equations through the entire annulus and all blade rows. Blade row turning, losses, and deviation were modeled using body force terms which required input data at stations between blade rows. The input data was calculated using a separate Navier-Stokes turbomachinery analysis code run at one operating point near stall, and was scaled to other operating points using overall characteristic maps. No information about the stalled characteristic was used. CSTALL was run in a 2-D throughflow mode for very fast calculations of operating maps and estimation of stall points. Calculated pressure ratio characteristics for NASA stage 35 agreed well with experimental data, and results with inlet radial distortion showed the expected loss of range. CSTALL was also run in a 3-D mode to investigate inlet circumferential distortion. Calculated operating maps for stage 35 with 120 degree distortion screens showed a loss in range and pressure rise. Unsteady calculations showed rotating stall with two part-span stall cells. The paper describes the body force formulation in detail, examines the computed results, and concludes with observations about the code.

Practical electron tomography

1995 ◽  
Vol 53 ◽  
pp. 742-743
Author(s):  
C.L. Woodcock
Keyword(s):  
Electron Tomography ◽  
Tomographic Reconstruction ◽  
Three Dimensional ◽  
3D Shape ◽  
Computational Resources ◽  
Shape Of Particles

Despite the potential of the technique, electron tomography has yet to be widely used by biologists. This is in part related to the rather daunting list of equipment and expertise that are required. Thanks to continuing advances in theory and instrumentation, tomography is now more feasible for the non-specialist. One barrier that has essentially disappeared is the expense of computational resources. In view of this progress, it is time to give more attention to practical issues that need to be considered when embarking on a tomographic project. The following recommendations and comments are derived from experience gained during two long-term collaborative projects.Tomographic reconstruction results in a three dimensional description of an individual EM specimen, most commonly a section, and is therefore applicable to problems in which ultrastructural details within the thickness of the specimen are obscured in single micrographs. Information that can be recovered using tomography includes the 3D shape of particles, and the arrangement and dispostion of overlapping fibrous and membranous structures.

A Three-Dimensional Viscous Transonic Inverse Design Method

2000 ◽  
Author(s):  
W. T. Tiow ◽  
M. Zangeneh
Keyword(s):  
Design Method ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Viscous Effects ◽  
Flow Equations ◽  
Flow Solution ◽  
Turbomachinery Blades ◽  
A Cell ◽  
Inverse Design Method ◽  
Euler Solver

The development and application of a three-dimensional inverse methodology is presented for the design of turbomachinery blades. The method is based on the mass-averaged swirl, rV~θ distribution and computes the necessary blade changes directly from the discrepancies between the target and initial distributions. The flow solution and blade modification converge simultaneously giving the final blade geometry and the corresponding steady state flow solution. The flow analysis is performed using a cell-vertex finite volume time-marching algorithm employing the multistage Runge-Kutta integrator in conjunction with accelerating techniques (local time stepping and grid sequencing). To account for viscous effects, dissipative forces are included in the Euler solver using the log-law and mixing length models. The design method can be used with any existing solver solving the same flow equations without any modifications to the blade surface wall boundary condition. Validation of the method has been carried out using a transonic annular turbine nozzle and NASA rotor 67. Finally, the method is demonstrated on the re-design of the blades.

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