Development of new curvature laws of the wall and a CFD-perturbation rotordynamic seal model /
Turbomachinery seals have extremely thin radial clearances between the stator and rotor which has a very large fluid-contacting area in the circumferential direction. The fluid passing the seals, therefore, experiences strong influence from the wall shear stress. Specific interests in the present st...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=730293871&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Turbomachinery seals have extremely thin radial clearances between the stator and rotor which has a very large fluid-contacting area in the circumferential direction. The fluid passing the seals, therefore, experiences strong influence from the wall shear stress. Specific interests in the present study are, first, to establish advanced near-wall turbulence modeling precisely accounting for the curvature effects to the wall shear stress on the rotor and stator of seals, and second, to develop a new perturbation CFD rotordynamic model taking into account the local shear stress disturbance of the whirling rotor. A two-dimensional streamline curvature law of the wall is analytically derived to include very strong curved-channel wall curvature effects through a novel perturbation analysis using a variable perturbation parameter. The new law allows improved analysis of such flows, and it provides the basis for improved wall function boundary conditions for their computation (CFD) over a wider range of y+, even for very strong curvature cases. Using the same variable perturbation parameter technique, a new law of the wall for swirling axial boundary layers is also derived accounting for the anisotropic eddy viscosity, and is implemented in the standard k-s model as a wall function. The new law gives CFD solutions in closer agreement with measurements than does the classical log-law. A new, quasi-three-dimensional perturbation model is developed for the computation of rotordynamic forces and moments of turbomachinery liquid seals. The model assumes small circular eccentric whirling motion of the rotor around the stator center. The perturbation of the dependent variables is made to account for the disturbed wall shear stresses and other quantities caused by the whirling motion of the rotor. The primary advantages of the present model are that firstly, it can be applied to any radial clearance seal of axisymmetric geometry and secondly, tilted whirling motion of the rotor can be described without any modification. |
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| Item Description: | Vita. "Major Subject: Mechanical Engineering". |
| Physical Description: | xxi, 166 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 136-145). |