No description available.

No description available.

No description available.

Thesis (M.S.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (leaf 70).

Thesis (M.A. Sc.)--University of Toronto, 2006. / Source: Masters Abstracts International, Volume: 45-03, page: 1546.

Few experiments have been carried out in the past to deter mine the effect of the lift and the drag forces on the trajectory of a ball used in any game. In a baseball game, it was reported that sometimes the ball took a sharp turn aburptly in the region of 15 to 20 feet from the home plate. This indicated a sudden change of the forces acting on the ball. The principal forces acting w ere as fol lows: 1. Weight of the ball. 2. Drag force acting in the direction parallel to the relative wind. 3. Lift force acting perpendicular to the relative wind.

Comparisons have been made between a general three-dimensional characteristics solution and available experimenta1 data with regard to the pressure distributions and force and moment coefficients for a spherically-capped 9-degree semivertex angle circular cone, up to angles of attack of 20 degrees. Also, predictions were computed using modified Newtonian theory since this theory has been widely used for bodies flying at hypersonic speeds. Several significant results have been found fran these comparisons. These are briefly summarized in the following statements: 1. The GASL program is adequate to the task of predicting the inviscid pressure distribution and the resultant aerodynamic forces for bodies at angle of attack. 2.The irregularities that occur in the GASL solution on the leeward side of a body at large angle of attack may limit its applicability in its present form to small angles of attack. For the blunt cone body considered here it appears that a 10-degree angle of attack would be an upper limit of applicability. 3. The GASL program represents a new capability which can be employed to begin a more rigorous analysis of the viscous effects which are known to be prevalent in the hypersonic speed range. 4. Only under very special conditions is modified Newtonian theory useful. Inasmuch as these conditions are defined in only general terms, no reasonable range of applicability can be stated. In those cases where it is employed, reliability remains to be proven, In the present application the method was shown to be unreliable. 5. The GASL program represents a first step towards the ability to compute the supersonic inviscid flow field about bodies at angle of attack, both for the study of inviscid and viscous flow fields. However, if progress is to be made towards a complete understanding of these flow fields, the problems revealed in the present comparisons would indicate that much more research and analysis is required. / Master of Science

<p>An explicit algebraic Reynolds stress model (EARSM) based ona pressure strain rate model including terms tensoriallynonlinear in the mean velocity gradients is developed in orderto improve predictions for .ows with strong curvature and/orrotation. This work has been carried out in the context of acollaborative international project on high-lift aerodynamics.For 2D mean .ows the nonlinear terms can easily be accountedfor in the model formulation. This is not the case for 3D mean.ows and approximations making the 2D and 3D mean .owformulations consistent are suggested. The proposed EARSM, theparent-EARSM and the corresponding di.erential Reynolds stressmodels (DRSM) are tested for spanwise rotating channel .ow andaxially rotating pipe .ow. The model predictions are comparedto experimental and DNS data. The nonlinear extensions areshown to have a signi.cant e.ect on the .ow predictions,somewhat less pronounced for the DRSM though. The turbulentdi.usion modelling in the EARSM computations is important forthe rotating pipe. It is shown that by using a Daly and Harlowdi.usion model, turbulence levels in good agreement withexperiments and DRSM can be achieved. However, by using asimpler e.ective eddy viscosity based di.usion model theturbulence kinetic energy levels are drastically overpredicted.Finally the proposed EARSM is tested on a standard high-liftcon.guration. The EARSM predictions are compared withexperiments and the predictions made by the standard K - ωtwo-equation model.</p><p><b>Descriptors:</b>Turbulence model, nonlinear modelling,streamline curvature, high-lift aerodynamics.</p>

A numerical procedure is presented which uses the truncation error injection methodology to efficiently achieve accurate approximations to complex problems having disparate length scales in the context of solving viscous, transonic flow over an airfoil. The truncation error distribution is estimated using the solution on a coarse grid. Local fine grids are formed which improve the resolution in regions of large truncation error. A fast fourth-order accurate scheme is presented for interpolating and relating the solutions between the generalized curvilinear coordinate systems of the local and global grids. It is shown that accurate solutions can be obtained on a global coarse grid with correction information obtained on local fine grids, which may or may not be topologically similar to the global grid as long as they are capable of resolving the local length scale. Dirichlet boundary conditions for the local grid yield the best results. The scheme also serves as the basis of a local refinement technique wherein a grid local to the nose of an airfoil is used to resolve a supersonic zone terminated by a shock and its interaction with a turbulent boundary layer. The solution on the local grid reveals details of the shock structure and a jet-like flow emanating from the root of the normal shock in the shock boundary layer interaction zone.

Dynamic stall characteristics of an NACA-0012 airfoil were investigated to assess the possibility of augmented lift during sinusoidal angle of attack motion. Tests were conducted over a range of Reynolds numbers from 2.0x10^5 to 5.0x10^5 and reduced frequencies from 0.02 to 0.3. The data were recorded and plotted in a series of lift coefficient vs. angle of attack diagrams. These diagrams exhibited a hysteresis curve for the dynamic stall cycle similar to the results of previous investigators but without a large peak at high angles of attack. The data were also plotted with lift coefficient vs. angular cycle position. The average lift coefficient was computed for each set of test conditions and plotted with average lift coefficient vs. reduced frequency for each value of Reynolds number. The summary data indicate an increase of average lift coefficient with reduced frequency, and increased Reynolds number, althought the increase was not monotonic.