| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 94 === We study the energy dissipation of two-dimensional granular gas using a high speed photography. In the first experiment, stainless steel spheres are used to fall along the inside wall of a hemispheric shell into a horizontal plate where they collid with each other and the average kinetic energy per particle was measured.
We find that the average kinetic energy per particle (E) of the granular gas decaies exponentially in E = E_0*e^{-r_d*tau} and decay rate(r_d) is predicted 0.7.
However, in computer simulation, decay rete(r_d) is about 0.23. We find that energy dissipates more rapidly in the experimental systems than that of the simulation, due in large part to the interactions of the particles with surface and glass baffle.
In the second experiment, we use a projectile at various inlet velocities (u_(0x)) and positions(b) to collided granular matrix which comprises stainless steel spheres.
We find that velocity of projectile (u_x) decaies exponentially in u_x = u_(0x)*e^{Gamma*t} where Gamma is decay time.
In the case of b = 2.75 mm, decay time decreases with the increasing of inlet velocity and a fitted formula is found, Gamma = a-b*u_(0x). Finally, we find that theoretical and experimental results for decay time are very close.
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