【国際交流・公開研究セミナー】Application of Finite Element Method Towards Understanding Flows
講演者:tProf. Sanjay Mittal(India, Indian Institute of Technology Kanpur)
Prof. Sanjay Mittal(India, Indian Institute of Technology Kanpur)が来日される機会に,同氏が最近展開している、「高精度な数値シミュレーション手法による移動境界を伴う物体周りの流れ現象の詳細な理解と解明」に関するご講演をお願いしました.是非ご参集ください.
アブストラクト:
A summary of our recent research efforts to understand fluid flows, by using computational methods, is presented. Stabilized finite element methods are employed to compute fluid flows at various Reynolds and Mach numbers including those that involve moving boundaries. Some of the flow problems arise from practical applications while others add to understanding of certain fundamental issues in fluid mechanics. Several examples that lead to physical understanding of flows will be presented.
Air-intake is an important hardware in the propulsion unit of supersonic aircrafts and missiles. The free-stream supersonic flow has to be slowed down such that the pressure recovery is maximum and flow distortion is minimal. For maximum efficiency one would like the oblique shocks to be followed by a weak normal shock that is located as close to the throat as possible. However, the shock should remain downstream of the throat from stability considerations. Results will be presented to show instability in such flows.
A circular cylinder, mounted on lightly damped springs, is allowed to to vibrate in both in-line and cross-flow directions. Computations have been carried out for Reynolds number in the laminar range. In most cases the trajectory of the cylinder corresponds to a Lissajou figure of 8. Lock-in is observed for a range of values of the structural frequency. The effect of mass of the cylinder and the blockage of the channel plays an important role in determining if the cylinder response is hysteretic.
Computations for two-dimensional flow past a stationary NACA0012 airfoil are carried out with progressively increasing and decreasing angles of attack. Our computations not only predict the phenomenon of stall but also pick-up the associated hysteresis close to the stall angle. The ability of the flow to remember its past history is responsible for its hysteretic behavior. The method has also been applied to multi-element airfoils that are deployed during take-off and landing.
Several questions about bluff body flows still remain unanswered. For example, what is the genesis of vortex shedding? What causes transition of boundary layer? What is the critical Reynolds number for the onset of instability of the shear layer. Some of our research efforts are directed to address these issues.
The leading edge cut causes the flow past a parafoil to become unsteady and leads to a significant loss in lift and increase in drag. The flow inside the parafoil cell remains almost stagnant resulting in a high value of pressure that is responsible for giving the parafoil its shape. The value of the lift-to-drag ratio obtained with the present computations is in good agreement with those reported in the literature. The effect of the size and location of the leading edge cut is studied.
連絡先:中央大学理工学部土木工学科
樫山 和男
電話: 03-3817-1808