颗粒介质中低速正碰撞驱动脉冲的传播与衰减
Propagation and attenuation of pulses driven by low velocity normal impacts in granular media
摘要：
我们进行了实验的低速正常的冲击到颗粒状材料，填充一个近似圆柱形的42升浴缸。颗粒介质中的运动用7个嵌入式加速度计的阵列跟踪。由撞击激发的纵向脉冲衰减，其形状变宽，并随着距离撞击点的行进距离而变得更平滑。脉冲传播不是关于撞击点的球对称。脉冲向下传播的峰值幅度大约是与垂直方向成45度传播的脉冲的两倍。一个对流扩散模型被用来估计脉冲特性的依赖性作为一个功能的旅行距离从网站的影响。脉冲峰值压力、速度和地震能量的幂律形式取决于从撞击到-2.5次方的距离，并且这种快速衰减与我们的实验测量大致一致。我们的实验支持地震震动模型，使冲击产生的地震能量迅速衰减到碎石小行星，而不是混响模型，地震能量缓慢衰减。我们应用我们的扩散模型来估计地震脉冲的物理特性，将激发即将到来的DART任务的影响到二次，Dimorphos，小行星二进制（65803）Didymos系统。我们估计，脉冲峰值加速度将超过表面重力，因为它通过小行星旅行。
英文摘要：
We carry out experiments of low velocity normal impacts into granular materials that fill an approximately cylindrical 42 litre tub. Motions in the granular medium are tracked with an array of 7 embedded accelerometers. Longitudinal pulses excited by the impact attenuate and their shapes broaden and become smoother as a function of travel distance from the site of impact. Pulse propagation is not spherically symmetric about the site of impact. Peak amplitudes are about twice as large for the pulse propagating downward than at 45 degrees from vertical. An advection-diffusion model is used to estimate the dependence of pulse properties as a function of travel distance from the site of impact. The power law forms for pulse peak pressure, velocity and seismic energy depend on distance from impact to a power of -2.5 and this rapid decay is approximately consistent with our experimental measurements. Our experiments support a seismic jolt model, giving rapid attenuation of impact generated seismic energy into rubble asteroids, rather than a reverberation model, where seismic energy slowly decays. We apply our diffusive model to estimate physical properties of the seismic pulse that will be excited by the forthcoming DART mission impact onto the secondary, Dimorphos, of the asteroid binary (65803) Didymos system. We estimate that the pulse peak acceleration will exceed the surface gravity as it travels through the asteroid.
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