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dc.contributor.authorPRZYBYTKOWSKI, STANISLAW MACIEY.
dc.creatorPRZYBYTKOWSKI, STANISLAW MACIEY.en_US
dc.date.accessioned2011-10-31T18:12:55Zen
dc.date.available2011-10-31T18:12:55Zen
dc.date.issued1983en_US
dc.identifier.urihttp://hdl.handle.net/10150/186568en
dc.description.abstractVarious sources of error can cause discrepancies among flight test results, experimental measurements and numerical predictions in the transonic regime. For unsteady flow, the effects of wind tunnel walls or a finite computational domain are the least understood and perhaps the most important. Although various techniques can be used in steady wind tunnel testing to minimize wall reflections, e.g., using slotted walls with ventilation, wind tunnel wall effects remain in unsteady wind tunnel testing even when they have been essentially eliminated from the steady flow. Even when the walls are ten chord lengths or more from the airfoil being tested, they can have a substantial effect on the unsteady aerodynamic response of the airfoil. In this study we compare numerical computations of two- and three-dimensional unsteady transonic flow with one another, and with experimental measurements, to isolate and examine the effects of tunnel walls. An extension of the time-linearized code developed by Fung, Yu and Seebass (1978) is used to obtain numerical results in two dimensions for comparison with one another and with the experimental measurments of Davis and Malcolm (1980). The steady flow which is perturbed by small unsteady airfoil motions is found numerically by specifying the pressure distribution rather than the airfoil coordinates using the procedure provided by Fung and Chung (1982). This provides results that are nearly free from effects caused by the small perturbation approximation; it also simulates the viscous effects present in the experimental measurements. A similar algorithm, developed especially for this study, is used for the related investigations in three dimensions. Different wall conditions are simulated numerically. Aside from a shift of frequency due to nonlinear effects, our numerical predictions of resonance conditions in two dimensions agree very well with those of linear acoustic theory. A substantial discrepancy between unconfined computations and wind tunnel experiments is observed in the low frequency range. This discrepancy highlights the importance of wall interference and wind tunnel measurements of unsteady transonic flows and delineates the conditions required to suppress them satisfactorily.
dc.language.isoenen_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.subjectAerodynamics, Transonic -- Mathematical models.en_US
dc.subjectTransonic wind tunnels -- Mathematical models.en_US
dc.subjectWind tunnels -- Mathematical models.en_US
dc.titleEFFECTS OF WALL INTERFERENCE ON UNSTEADY TRANSONIC FLOWS.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.contributor.chairSeebass, A. R.en_US
dc.identifier.oclc689058121en_US
thesis.degree.grantorUniversity of Arizonaen_US
thesis.degree.leveldoctoralen_US
dc.contributor.committeememberFung, K. Y.Sears, W. R.en_US
dc.identifier.proquest8319730en_US
thesis.degree.disciplineApplied Mathematicsen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.namePh.D.en_US
refterms.dateFOA2018-08-23T14:16:04Z
html.description.abstractVarious sources of error can cause discrepancies among flight test results, experimental measurements and numerical predictions in the transonic regime. For unsteady flow, the effects of wind tunnel walls or a finite computational domain are the least understood and perhaps the most important. Although various techniques can be used in steady wind tunnel testing to minimize wall reflections, e.g., using slotted walls with ventilation, wind tunnel wall effects remain in unsteady wind tunnel testing even when they have been essentially eliminated from the steady flow. Even when the walls are ten chord lengths or more from the airfoil being tested, they can have a substantial effect on the unsteady aerodynamic response of the airfoil. In this study we compare numerical computations of two- and three-dimensional unsteady transonic flow with one another, and with experimental measurements, to isolate and examine the effects of tunnel walls. An extension of the time-linearized code developed by Fung, Yu and Seebass (1978) is used to obtain numerical results in two dimensions for comparison with one another and with the experimental measurments of Davis and Malcolm (1980). The steady flow which is perturbed by small unsteady airfoil motions is found numerically by specifying the pressure distribution rather than the airfoil coordinates using the procedure provided by Fung and Chung (1982). This provides results that are nearly free from effects caused by the small perturbation approximation; it also simulates the viscous effects present in the experimental measurements. A similar algorithm, developed especially for this study, is used for the related investigations in three dimensions. Different wall conditions are simulated numerically. Aside from a shift of frequency due to nonlinear effects, our numerical predictions of resonance conditions in two dimensions agree very well with those of linear acoustic theory. A substantial discrepancy between unconfined computations and wind tunnel experiments is observed in the low frequency range. This discrepancy highlights the importance of wall interference and wind tunnel measurements of unsteady transonic flows and delineates the conditions required to suppress them satisfactorily.


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