2017年刘天舒教授暑期赴西华大学短期讲学安排
报告人：刘天舒教授
美国西密西根大学机械与航空工程系主任、空气动力测量技术专家
报告时间：2017年8月2日 9：00
报告地点：西华大学行政楼212会议室
刘天舒教授简介：
Tianshu Liu
Professor
Department of Mechanical and Aerospace Engineering
Western Michigan University, Kalamazoo
Research interests:
lAerodynamics
lFluid mechanics
lHeat transfer
Short Biography:
Tianshu Liu is a professor and the director of Applied Aerodynamics Laboratory at Western Michigan University (Kalamazoo, Michigan, USA). He received a Ph.D. in aeronautics and astronautics from Purdue University (West Lafayette, Indiana, USA) in 1996. He was a research scientist at NASA Langley Research Center (Hampton, Virginia, USA) in 1999-2004. His research areas cover experimental and applied aerodynamics, and theoretical aerodynamics models. In particular, he has contributed to image-based aerodynamic measurement techniques for various physical quantities such as surface pressure, temperature/heat-transfer, skin friction, velocity fields, aeroelastic deformation and distributed and integrated forces. Other topics include videogrammetry and vision for aerospace applications, flow control, flapping flight, flight vehicle design, transition and turbulence, flight tests, and bias error theory.
Abstracts for Presentations:
1. Camera Calibration at Large Scene
Camera calibration is a key procedure in photogrammetric or videogrammetric measurements for various engineering applications including deformation, model attitudes and positions. This talk discusses the relevant issues on camera calibration at large scene that is difficult since a known target field is not easy to be established. The principles on camera calibration/orientation are reviewed, and several methods are discussed including the bundle-adjustment method, the direct-linear transformation, closed-form resection, and optimization method. Various examples are given.
2. Skin Friction Structures Extracted from Surface Pressure Gradient Field
This talk focuses on a recent study on how to extract skin-friction structures from pressure-sensitive paint (PSP) measurements. An intrinsic relation is first given between the skin-friction vector and the surface pressure gradient through the boundary enstrophy flux (BEF). The attempt contains two related parts. In the first part, when the BEF field is given, a projected skin-friction field in the image plane can be sought from a surface pressure image based on a variational solution of an optical-flow-like equation. This approach is validated in several classical flows. The second part deals with a practical problem in which the BEF field is not known a priori. In this case, a so-called auxiliary skin-friction field is determined from a surface pressure image alone by using the same variational approach. The auxiliary skin-friction field has the magnitude proportional to the skin-friction magnitude and the direction of the negative surface pressure gradient. The physical meaning of the auxiliary skin-friction field and its applicability to global skin-friction diagnostics are discussed. The latest effort is made to reconstruct the near-wall flow structures by using a combination of this developed method and the series expansion of the Navier-Stoke equations.
3. Global Skin Friction Diagnostics Using Temperature Sensitive Paint
This talk discusses the principle of global skin friction diagnostics based on temperature sensitive paint (TSP) measurements in flows. The asymptotic form of the energy equation at a wall is derived, and its inverse solution is sought by using the variational method to extract a relative or normalized skin friction field from TSP-measured surface temperature fields. The selection of the relevant parameters (the Lagrange multiplier and the standard deviation of a Gaussian filter) and the intrinsic limitations of this method are discussed in the light of uncertainty analysis. Experimental implementation of this method is described, and the feasibility of TSP-based global skin friction diagnostics is examined in impinging jet experiments. The normalized skin friction distributions extracted by using this method are in fairly good agreement with hot-film skin friction measurements and the theoretical solutions in the normal and oblique impinging jets. In particular, a recent example is given on the skin-friction diagnostics in the complex separated flow over a circular cylinder in water flow.
