Unsteady aerodynamic loading produced by a sinusoidally oscillating delta wing

The effect of the unsteady aerodynamic loading of oscillating airfoils in the low-reduced frequency regime on the work per cycle curves is investigated. The theoretical analysis is based on a perturbation analysis of the linearized Navier–Stokes equations for real modes at low-reduced frequency. It was discovered that a new parameter, the unsteady loading, plays an essential role in the trends of the phase and modulus of the unsteady pressure caused by the airfoil oscillation. Here, the theory is extended in order to quantify this new parameter. It is shown that this parameter depends solely on the steady flow-field on the airfoil surface and the vibration mode-shape. As a consequence, the effect of changing the design operating conditions or the vibration mode onto the work-per-cycle curves (and therefore in the stability) can be easily predicted and, what is more important, quantified without conducting additional flutter analysis. The relevance of the parameter has been numerically confirmed in the Part II of the paper.

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Experimental Investigation of Multistage Interaction Gust Aerodynamics

Journal of Turbomachinery ◽

10.1115/1.3262288 ◽

1989 ◽

Vol 111 (4) ◽

pp. 409-417 ◽

Cited By ~ 9

Author(s):

V. R. Capece ◽

S. Fleeter

Keyword(s):

Axial Flow ◽

Unsteady Aerodynamics ◽

Unique Data ◽

Aerodynamic Loading ◽

Unsteady Aerodynamic ◽

Forcing Function ◽

Reduced Frequency ◽

Aerodynamic Interaction ◽

Blade Row ◽

Potential Interactions

The fundamental flow physics of multistage blade row interactions are experimentally investigated at realistic reduced frequency values. Unique data are obtained that describe the fundamental unsteady aerodynamic interaction phenomena on the stator vanes of a three-stage axial flow research compressor. In these experiments, the effect on vane row unsteady aerodynamics of the following are investigated and quantified: (1) steady vane aerodynamic loading; (2) aerodynamic forcing function waveform, including both the chordwise and transverse gust components; (3) solidity; (4) potential interactions; and (5) isolated airfoil steady flow separation.

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Aerodynamic Damping Predictions for Oscillating Airfoils in Cascades Using Moving Meshes

Volume 7B: Structures and Dynamics ◽

10.1115/gt2016-57017 ◽

2016 ◽

Cited By ~ 3

Author(s):

Ron Ho Ni ◽

William Humber ◽

Michael Ni ◽

Vincent R. Capece ◽

Michael Ooten ◽

...

Keyword(s):

Experimental Data ◽

Numerical Solutions ◽

Harmonic Balance Method ◽

Standard Test ◽

Influence Coefficient ◽

Flow Conditions ◽

Suction Surface ◽

Test Configuration ◽

Aerodynamic Loading ◽

Unsteady Aerodynamic

This paper presents a numerical analysis of oscillating airfoils in turbomachinery cascades using the unsteady nonlinear Reynold’s Averaged Navier-Stokes (URANS) equations. The periodic unsteady flow solutions are determined using a conventional time marching method (DTS) and the Nonlinear Harmonic Balance method (NHB). Mesh motions, using a weighted distortion procedure and a linear elastic method, are described. Comparison of computed results are made with the Eleventh Standard Test Configuration (STC11) experimental data for subsonic and transonic exit flow conditions. The solutions for the NHB and DTS methods exhibit excellent correlation with each other and good correlation with the experimental data on the pressure surface. The numerical solutions deviate from the experimental data on the suction surface especially in the vicinity of the shock wave for the transonic exit flow case. A numerical influence coefficient modeling method is shown for airfoil cascades that can be used to calculate unsteady aerodynamic loading over a range of interblade phase angles. Application to the STC11 illustrates that a cascade of five airfoils is sufficient to provide accurate unsteady aerodynamic loading predictions for the modeled flow conditions.

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Numerical Computation of Unsteady Flows at Low Frequencies in the Last Stage of a Steam Turbine

Volume 1: Turbomachinery ◽

10.1115/87-gt-143 ◽

1987 ◽

Author(s):

R. Lattermann ◽

J. Wachter

Keyword(s):

Steam Turbine ◽

Flow Model ◽

Turbine Stage ◽

Asymmetric Flow ◽

Order Accuracy ◽

Low Frequencies ◽

Aerodynamic Loading ◽

Unsteady Aerodynamic ◽

Time Marching ◽

Last Stage

The asymmetric flow field downstream the final stage of steamturbines causes an unsteady aerodynamic loading of the rotor in the range of the lower blade eigenfrequencies. A numerical solution for the time-dependent Euler equations is presented for a complete turbine stage, varying the outlet pressure sinusoidally in the rotating frame of reference. A two-dimensional blade-to-blade flow model is used including variable streamsheet thickness and changing radii. The equations are solved by an explicit time-marching finite difference algorithm of second order accuracy in space and time. Additionally the quasi-steady solution is compared with measurements in a model steam turbine.

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