TURNS: A Free-Wake Eule/Navier-Stokes Numerical Method for Helicopter Rotors

Database of full-scale three-dimensional sail shapes are presented with the aerodynamic coefficients for the upwind condition of IMS type sails. Three-dimensional shape data are used for the input of numerical calculations and the results are compared with the measured sail performance. The sail shapes and performance are measured using a sail dynamometer boat Fujin. The Fujin is a 34-foot LOA boat, in which load cells and charge coupled devices (CCD) cameras are installed to measure the sail forces and shapes simultaneously. The sailing conditions of the boat, such as boat speed, heel angle, wind speed, wind angle, and so on, are also measured. The tested sail configurations are as follows: mainsail with 130% jib, mainsail with 75% jib and mainsail alone. Sail shapes are measured at several height positions. The measured shape parameters are chord length, maximum draft, maximum draft position, entry angle at the luff and exit angle at the leech. From these parameters three-dimensional coordinates of the sails are calculated by interpolation. These three-dimensional coordinates are tabulated with the aerodynamic coefficients. Numerical calculations are performed using the measured sail shapes. The calculation methods are of two types; Reynolds-averaged Navier-Stokes (RANS)-based CFD and vortex lattice methods (VLM). A multi-block RANS-based CFD method was developed by one of the authors and is capable of predicting viscous flows and aerodynamic forces for complicated sail configuration for upwind as well as downwind conditions. Important features of the numerical method are summarized as follows: a Finite- Analytic scheme to discretize transport equations, a PISO type velocity-pressure coupling scheme, multi-block domain decomposition capability, and several choices of turbulence models depending on flows of interest. An automatic grid generation scheme is also included. Another calculation method, the vortex lattice method is also adopted. In this case, step-by-step calculations are conducted to attain the steady state of the sail in steady wind. Wake vortices are generated step-by-step, which flow in the direction of the local velocity vector. These calculated sail forces are compared with the measured one, and the validity of the numerical method is studied. The sail shape database and comparison with numerical calculations will provide a good benchmark for the sail performance analysis of the upwind condition of IMS type sails.

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Flowfield Analysis of Modern Helicopter Rotors in Hover by Navier‐Stokes Method

Journal of the American Helicopter Society ◽

10.4050/jahs.38.3.3 ◽

1993 ◽

Vol 38 (3) ◽

pp. 3-13 ◽

Cited By ~ 34

Author(s):

G. R. Srinivasan ◽

V. Raghavan ◽

E. P. N. Duque ◽

W. J. McCroskey

Keyword(s):

Navier Stokes ◽

Helicopter Rotors

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A Navier-Stokes/full potential/free wake method for rotor flows

10.2514/6.1997-401 ◽

1997 ◽

Cited By ~ 7

Author(s):

Mert Berkman ◽

Lakshmi Sankar ◽

Charles Berezin ◽

Michael Torok ◽

Mert Berkman ◽

...

Keyword(s):

Navier Stokes ◽

Full Potential ◽

Free Wake

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Radial Turbine Rotor Response to Pulsating Inlet Flows

Journal of Turbomachinery ◽

10.1115/1.4025948 ◽

2013 ◽

Vol 136 (7) ◽

Cited By ~ 10

Author(s):

Teng Cao ◽

Liping Xu ◽

Mingyang Yang ◽

Ricardo F. Martinez-Botas

Keyword(s):

Numerical Method ◽

Time Lag ◽

Turbine Rotor ◽

Pulsating Flow ◽

Navier Stokes ◽

Transient Effects ◽

Flow Conditions ◽

Radial Turbine ◽

Reduced Frequency ◽

Integrated Performance

The performance of automotive turbocharger turbines has long been realized to be quite different under pulsating flow conditions compared to that under the equivalent steady and quasi-steady conditions on which the conventional design concept is based. However, the mechanisms of this phenomenon are still intensively investigated nowadays. This paper presents an investigation of the response of a stand-alone rotor to inlet pulsating flow conditions by using a validated unsteady Reynolds-averaged Navier–Stokes solver (URANS). The effects of the frequency, the amplitude, and the temporal gradient of pulse waves on the instantaneous and cycle integrated performance of a radial turbine rotor in isolation were studied, decoupled from the upstream turbine volute. A numerical method was used to help gain the physical understanding of these effects. A validation of the numerical method against the experiments on a full configuration of the turbine was performed prior to the numerical tool being used in the investigation. The rotor was then taken out to be studied in isolation. The results show that the turbine rotor alone can be treated as a quasi-steady device only in terms of cycle integrated performance; however, instantaneously, the rotor behaves unsteadily, which increasingly deviates from the quasi-steady performance as the local reduced frequency of the pulsating wave is increased. This deviation is dominated by the effect of quasi-steady time lag; at higher local reduced frequency, the transient effects also become significant. Based on this study, an interpretation and a model of estimating the quasi-steady time lag have been proposed; a criterion for unsteadiness based on the temporal local reduced frequency concept is developed, which reduces to the Λ criterion proposed in the published literature when cycle averaged. This in turn emphasizes the importance of the pressure wave gradient in time.

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Validation of a Numerical Method for Unsteady Flow Calculations

Journal of Turbomachinery ◽

10.1115/1.2929195 ◽

1993 ◽

Vol 115 (1) ◽

pp. 110-117 ◽

Cited By ~ 25

Author(s):

M. Giles ◽

R. Haimes

Keyword(s):

Heat Transfer ◽

Flat Plate ◽

Numerical Method ◽

Stokes Equations ◽

Companion Paper ◽

Ideal Gas ◽

Euler Method ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Loss Prediction

This paper describes and validates a numerical method for the calculation of unsteady inviscid and viscous flows. A companion paper compares experimental measurements of unsteady heat transfer on a transonic rotor with the corresponding computational results. The mathematical model is the Reynolds-averaged unsteady Navier–Stokes equations for a compressible ideal gas. Quasi-three-dimensionality is included through the use of a variable streamtube thickness. The numerical algorithm is unusual in two respects: (a) For reasons of efficiency and flexibility, it uses a hybrid Navier–Stokes/Euler method, and (b) to allow for the computation of stator/rotor combinations with arbitrary pitch ratio, a novel space–time coordinate transformation is used. Several test cases are presented to validate the performance of the computer program, UNSFLO. These include: (a) unsteady, inviscid flat plate cascade flows (b) steady and unsteady, viscous flat plate cascade flows, (c) steady turbine heat transfer and loss prediction. In the first two sets of cases comparisons are made with theory, and in the third the comparison is with experimental data.

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