A Double-Passage Shape Correction Method for Predictions of Unsteady Flow and Aeroelasticity in Turbomachinery

2017 ◽  
Vol 9 (4) ◽  
pp. 839-860 ◽  
Author(s):  
Tongqing Guo ◽  
Di Zhou ◽  
Zhiliang Lu
Keyword(s):  
Unsteady Flow ◽  
Turbulent Flows ◽  
Fourier Coefficients ◽  
Three Dimensional ◽  
Correction Method ◽  
Solution Stability ◽  
Shape Correction ◽  
Flow Variables ◽  
Transonic Fan ◽  
Solution Accuracy

AbstractIn this paper, a double-passage shape correction (DPSC) method is presented for simulation of unsteady flows around vibrating blades and aeroelastic prediction. Based on the idea of phase-lagged boundary conditions, the shape correction method was proposed aimed at efficiently dealing with unsteady flow problems in turbomachinery. However, the original single-passage shape correction (SPSC) may show the disadvantage of slow convergence of unsteady solutions and even produce nonphysical oscillation. The reason is found to be related with the disturbances on the circumferential boundaries that can not be damped by numerical schemes. To overcome these difficulties, the DPSC method is adopted here, in which the Fourier coefficients are computed from flow variables at implicit boundaries instead of circumferential boundaries in the SPSC method. This treatment actually reduces the interaction between the calculation of Fourier coefficients and the update of flow variables. Therefore a faster convergence speed could be achieved and also the solution stability is improved. The present method is developed to be suitable for viscous and turbulent flows. And for real three-dimensional (3D) problems, the rotating effects are also considered. For validation, a 2D oscillating turbine cascade, a 3D oscillating flat plate cascade and a 3D practical transonic fan rotor are investigated. Comparisons with experimental data or other solutions and relevant discussions are presented in detail. Numerical results show that the solution accuracy of DPSC method is favorable and at least comparable to the SPSC method. However, fewer iteration cycles are needed to get a converged and stable unsteady solution, which greatly improves the computational efficiency.

Prediction of Flutter and Inlet Distortion Driven Response of a Transonic Fan Rotor Using Phase-Lagged Boundary Conditions

2001 ◽  
Author(s):  
H. D. Li ◽  
L. He
Keyword(s):  
Computing Time ◽  
Three Dimensional ◽  
Correction Method ◽  
Forced Response ◽  
Navier Stokes ◽  
Design Environment ◽  
Inlet Distortion ◽  
Single Passage ◽  
Shape Correction ◽  
Transonic Fan

Prediction of blade forced response and flutter is of great importance to turbomachinery designers. However, calculations of unsteady turbomachinery flows using conventional time-domain methods typically would lead to the use of multi-passage/whole-annulus domains due to the required direct periodic condition. This makes numerical computations extremely time-consuming and is one of the major difficulties for nonlinear unsteady calculations to be applied in a blading design environment. A single-passage approach to three-dimensional unsteady Navier-Stokes calculations using the Fourier-series based Shape-Correction method has been developed, and been applied to analyze inlet distortion driven response and flutter of a transonic fan rotor (NASA Rotor-67). The key feature is that the Shape-Correction method enables a single-passage solution to unsteady flows in blade rows under influences of multiple disturbances with arbitrary inter-blade phase angles. The results show that the single-passage solution can capture deterministic unsteadiness as well as time-averaged flows in good agreement with conventional multi-passage solutions, while the corresponding computing time can be reduced dramatically.

Three-Dimensional Wake Decay Inside of a Compressor Cascade and Its Influence on the Downstream Unsteady Flow Field: Part II—Unsteady Flow Field Downstream of the Stator

1991 ◽  
Vol 113 (2) ◽  
pp. 190-197 ◽  
Author(s):  
C. Poensgen ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Turbulent Flows ◽  
Velocity Vector ◽  
Three Dimensional ◽  
Time Dependent ◽  
Major Influence ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Turbulent Flow Field

A measuring technique based on multisensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In Part I of this paper the decay of the rotor wakes has been described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II of this paper. The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of the paper.

Three-Dimensional Wake Decay Inside of a Compressor Cascade and its Influence on the Downstream Unsteady Flow Field: Part II — Unsteady Flow Field Downstream of the Stator

1990 ◽  
Author(s):  
C. Poensgen ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Turbulent Flows ◽  
Velocity Vector ◽  
Three Dimensional ◽  
Time Dependent ◽  
Major Influence ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Turbulent Flow Field

A measuring technique based on multi-sensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In Part I of this paper the decay of the rotor wakes will be described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II of this paper. The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of this paper.

scholarly journals A fish perspective: detecting flow features while moving using an artificial lateral line in steady and unsteady flow

2014 ◽  
Vol 11 (99) ◽  
pp. 20140467 ◽  
Author(s):  
L. D. Chambers ◽  
O. Akanyeti ◽  
R. Venturelli ◽  
J. Ježov ◽  
J. Brown ◽  
...  
Keyword(s):  
Unsteady Flow ◽  
Turbulent Flows ◽  
Lateral Line ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Frontal Plane ◽  
Flow Speed ◽  
Lateral Line System ◽  
Line System ◽  
Karman Vortex

For underwater vehicles to successfully detect and navigate turbulent flows, sensing the fluid interactions that occur is required. Fish possess a unique sensory organ called the lateral line. Sensory units called neuromasts are distributed over their body, and provide fish with flow-related information. In this study, a three-dimensional fish-shaped head, instrumented with pressure sensors, was used to investigate the pressure signals for relevant hydrodynamic stimuli to an artificial lateral line system. Unsteady wakes were sensed with the objective to detect the edges of the hydrodynamic trail and then explore and characterize the periodicity of the vorticity. The investigated wakes (Kármán vortex streets) were formed behind a range of cylinder diameter sizes (2.5, 4.5 and 10 cm) and flow velocities (9.9, 19.6 and 26.1 cm s −1 ). Results highlight that moving in the flow is advantageous to characterize the flow environment when compared with static analysis. The pressure difference from foremost to side sensors in the frontal plane provides us a useful measure of transition from steady to unsteady flow. The vortex shedding frequency (VSF) and its magnitude can be used to differentiate the source size and flow speed. Moreover, the distribution of the sensing array vertically as well as the laterally allows the Kármán vortex paired vortices to be detected in the pressure signal as twice the VSF.

Toward Intra-Row Gap Optimization for One and Half Stage Transonic Compressor

2005 ◽  
Vol 127 (3) ◽  
pp. 589-598 ◽  
Author(s):  
H. D. Li ◽  
L. He
Keyword(s):  
Computing Time ◽  
Three Dimensional ◽  
Correction Method ◽  
Aerodynamic Performance ◽  
Current Approach ◽  
Influence Coefficient ◽  
Transonic Compressor ◽  
Shape Correction ◽  
Gap Spacing ◽  
Gap Effects

Multistage effects on both aerodynamics and aeromechanics have been identified as significant. Thus, design optimizations for both aerodynamic performance and aeromechanical stability should be done in the unsteady multistage environment. The key issue preventing such a procedure to be carried out is the enormous computing time cost of multistage unsteady simulations. In this paper, a methodology based on the single-passage shape-correction method integrated with an interface disturbance truncation technique has been developed. The capability, efficiency, and accuracy of the developed methodology have been demonstrated for a one and a half stage quasi-three-dimensional transonic compressor with realistic blade counts. Furthermore, the interface disturbance truncation technique enables us to separate multirow interaction effects from the upstream and the downstream, which makes it possible to superimpose different rotor upstream gap effects and rotor downstream gap effects on the middle row rotor aerodynamic damping. In addition, a gap influence coefficient approach has been developed for investigation of all the possible gap spacing combinations of M upstream stator-rotor gaps and N downstream rotor-stator gaps. Then the number of cases that need to be computed has been reduced from M×N to M+N, which saved substantial computing time. The optimization analysis shows significant damping variation (∼300%) within the chosen intrarow gap design space. The intrarow gap spacing could have either stabilizing or destabilizing effects so that the stabilizing axial spacing could be utilized to increase flutter-free margin in aeromechanical designs. The current approach also can be used for setting aeromechanical constraints for aerodynamic performance optimizations.

Unsteady Flow Modeling Using Transient Rotor–Stator Interface

2013 ◽  
Author(s):  
Rudolf A. Izmaylov ◽  
Henry D. Lopulalan ◽  
Gertruida S. Norimarna
Keyword(s):  
Experimental Data ◽  
Unsteady Flow ◽  
Turbulent Flows ◽  
Reasonable Agreement ◽  
Full Range ◽  
Three Dimensional ◽  
Time Discretization ◽  
Rotating Stall ◽  
Flow Phenomena ◽  
Calculation Results

Based on experimental investigation of unsteady flow phenomena in centrifugal compressor, conducted in LPI (SPbSPU), including the measurements of high frequency pressure and hot-wire probes, numerical calculation was conducted with the aid of commercial ANSYS CFX12. The object was a model of industrial compressor, tested in full range of mass flows (from maximum to the onset of surge). Unsteady turbulent flows were calculated with URANS, turbulence model - SST-Menter. Region between the impeller and diffuser was calculated with Transient Method option. Time discretization Δ = 12 μsec. Sequential 20 revolutions of rotors were calculated, also LES model were used. Unsteady calculation results demonstrated reasonable agreement with experimental data both in meridional, and radial sections concerning the character of “jet – wakes” propagation, distribution of velocities in diffuser, and clearly showed three-dimensional flow conditions and reverse zones on the diffuser walls. “Frozen” velocity distributions during rotating stall demonstrated possibility of unsteady flow prediction with the aid of ANSYS CFX12. CFD results comparison with experimental data showed reasonable agreement for distributions of total pressures in diffuser, as well total and static characteristics of impeller and diffuser.

scholarly journals Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1079
Author(s):  
Lena Mahl ◽  
Patrick Heneka ◽  
Martin Henning ◽  
Roman B. Weichert
Keyword(s):  
Boundary Conditions ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Three Dimensional ◽  
Free Water ◽  
Lateral Wall ◽  
Lateral Spreading ◽  
Propagation Length ◽  
Vertical Slot ◽  
Surface Jets

The efficiency of a fishway is determined by the ability of immigrating fish to follow its attraction flow (i.e., its jet) to locate and enter the fishway entrance. The hydraulic characteristics of fishway entrance jets can be simplified using findings from widely investigated surface jets produced by shaped nozzles. However, the effect of the different boundary conditions of fishway entrance jets (characterized by vertical entrance slots) compared to nozzle jets must be considered. We investigate the downstream propagation of attraction jets from the vertical slot of a fishway entrance into a quiescent tailrace, considering the following boundary conditions not considered for nozzle jets: (1) slot geometry, (2) turbulence characteristics of the approach flow to the slot, and (3) presence of a lateral wall downstream of the slot. We quantify the effect of these boundary conditions using three-dimensional hydrodynamic-numeric flow simulations with DES and RANS turbulence models and a volume-of-fluid method (VoF) to simulate the free water surface. In addition, we compare jet propagation with existing analytical methods for describing jet propagations from nozzles. We show that a turbulent and inhomogeneous approach flow towards a vertical slot reduces the propagation length of the slot jet in the tailrace due to increased lateral spreading compared to that of a jet produced by a shaped nozzle. An additional lateral wall in the tailrace reduces lateral spreading and significantly increases the propagation length. For highly turbulent flows at fishway entrances, the RANS model tends to overestimate the jet propagation compared to the transient DES model.

Unsteady Three-Dimensional Analysis of Inlet Distortion in a Transonic Fan

2006 ◽  
Author(s):  
Peng Sun ◽  
Guotal Feng
Keyword(s):  
Shock Wave ◽  
Total Pressure ◽  
Large Scale ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Inlet Distortion ◽  
Flow Loss ◽  
Large Scale Vortex ◽  
Total Temperature ◽  
Transonic Fan

A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out using "Fluent-parallel" in a parallel supercomputer. The numerical simulation focused on a transonic fan with inlet square wave total pressure distortion and the analysis of result consisted of three aspects. The first was about inlet parameters redistribution and outlet total temperature distortion induced by inlet total pressure distortion. The pattern and causation of flow loss caused by pressure distortion in rotor were analyzed secondly. It was found that the influence of distortion was different at different radial positions. In hub area, transportation-loss and mixing-loss were the main loss patterns. Distortion not only complicated them but enhanced them. Especially in stator, inlet total pressure distortion induced large-scale vortex, which produced backflow and increased the loss. While in casing area, distortion changed the format of shock wave and increased the shock loss. Finally, the format of shock wave and the hysteresis of rotor to distortion were analyzed in detail.

Assessment of Unsteady Flows in Turbines

1992 ◽  
Vol 114 (1) ◽  
pp. 79-90 ◽  
Author(s):  
O. P. Sharma ◽  
G. F. Pickett ◽  
R. H. Ni
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Research Activities ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

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