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Hydrodynamic Simulation and Flow Pattern Analysis of Shark Undulation Motions

Ebrahimi Chamkakaei, Mohsen | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47099 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Abbaspour Tehrani Fard, Majid
  7. Abstract:
  8. Many species in nature exist which human can reach the aims of flying and swimming by inspiring from them. Observations show that fish can use their especial undulating motions of body/fins to crusing, increase performance, suddenly acceleration, and maneuvering. To design a robot fish and benefit the characteristics and abilities of a live fish, using its real geometry and kinematics in the robot is vital. Therefore, simulations are essential to better exploiting the fish behavior, which can obtain useful consequences by using computational fluid dynamics. In this thesis, first the kinematics of sharks is investigated. Then, investigations are accomplished by utilizing an unsteady finite volume method on a 2D cross section of shark. Comparisions are carried out with the conventional oscillating mechanisms and remarkable results from the analyzing of their performance, energy consumption, forces, efficiency, and wake structures are presented. Finally, 3D simulations of a shark geometry extracted from the real shark are presented. Some of the important findings are: the results show that the kinematic equation with 3 sinusoidal terms and a third order polynomial function of amplitude excursion show satisfiable accuracy to be chosen as the optimal kinematic equation. In addition, simullations show that although all of the oscillating mechanisms suffer from the losses originating form the lateral motions, the undulating mechanisms show considerably lower losses in comparison to the rigid body mechanisms. Furthermore, the vortical structures of wakes in oscillating mechanisms and especially undulating mechanism highly depend on the Strouhal number of oscillations. The wake of undulating body with the backward travelling waves through the body is more regular than other oscillating mechanisms and its dissipations are less. Also, in a given Reynolds number, the thrust force increases with the increasing of the amplitude and frequency of the oscillations. The maximum efficiency occurs in the frequency with the value close to the forward speed of the shark
  9. Keywords:
  10. Numerical Simulation ; Flow Patterns ; Undulatory Swimming ; Swimming Hydrodynamics ; Shark

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  • Comparative numerical analysis of the flow pattern and performance of a foil in flapping and undulating oscillations
    • Abstract
    • Introduction
    • Materials and methods
      • Fluid--solid interaction problem
      • Governing equations of fluid
      • Simulation algorithm
      • Solver
      • Mesh construction
      • Boundary conditions
      • Mesh motion and correction techniques
      • Kinematics
      • Wake visualization
    • Forces, consumed power, and efficiency calculations
      • Validation, grid dependency study, and time step
    • Results and discussions
      • Instantaneous inline and transverse forces, and pitching moment
      • Time-averaged inline force
      • Consumed power
      • Efficiency
      • Wake structures and surface pressure coefficient
    • Conclusions
    • Appendixes
      • Appendix 1: Calculation of forces, powers, normalized coefficients, and efficiency
    • Appendix 2: Validation of solver and grid dependency study
      • Validation of solver
      • Grid dependency
    • References
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