分数Maxwell黏弹性胶体阻尼缓冲器启动流模型

Fractional Maxwell Model of Start-up Flow for a Viscoelastic Elastomer Shock Absorber

针对黏弹性胶体在阻尼缓冲器中流动时黏弹性较强,用于模拟和研究阻尼缓冲器间隙流和孔隙流启动流模型较少的问题,提出一种含准态特性参数、用于研究黏弹性胶体阻尼缓冲器启动流的分数Maxwell模型。阻尼缓冲器阻尼孔和节流间隙中启动流的流动情况简化为圆管内加速流动和两平行板间一板不动、一板加速运动两种单向加速启动流形式,按照实际工况设立控制方程、初始值和边界条件,采用有限差分法求得分数Maxwell模型的数值解,并通过试验证明了模型的准确性。数值模拟和试验测试结果表明:分数Maxwell模型模拟的流体具有良好的黏弹性,其应力呈线性增长趋势;随着模型参数α、β和ζ的增加,分数Maxwell模型流速分布曲线曲率呈下降趋势;启动流试验测试系统捕捉到的黏弹性胶体在阻尼孔中启动流形状从扁平状发展为抛物线状,该结果与分数Maxwell模型模拟结果变化趋势相同;分数Maxwell模型模拟的流体最大液面高度和最大曲率距离与试验结果相吻合,最大误差分别为4.79%和4.67%,证明了所提出的分数Maxwell模型可准确地模拟黏弹性胶体在阻尼缓冲器的阻尼孔和节流间隙中的启动流特性。

The viscoelastic elastomer has a strong viscoelasticity when it flows inside a shock absorber.The start-up flow models for simulating and studying a viscoelastic elastomer in the orifice and gap of shock absorber have been rarely reported. A fractional Maxwell model with quasi-property is proposed to study the start-up flow of viscoelastic elastomer shock absorber. The start-up flows in the orifice and gap of shock absorber are simplified by unidirectional accelerated flows in a pipe and between two parallel plates of which one is accelerating and the other is at rest. The fractional Maxwell model is developed using finite difference method with real-world initial and boundary conditions. The eproposed model was proved by test. The numerical and test results indicate that the fluid simulated by the fractional Maxwell model had good viscoelasticity,and its stress increase linearly;the curvatures of flow velocity distribution curve of Maxwell model decrease with the increase in the model parameters α,β and ζ;the shape of start-up flow of viscoelastic elastomer in the orifice captured by the test system evolves from a flat shape to a parabolic shape,of which the variation trend is the same as with the result simulated by the fractional Maxwell model;and the simulated maximum fluid level and maximum curvature distance of the fractional Maxwell model are in good agreement with the test results. The maximum errors are 4. 79% and 4. 67%,respectively. The results show that the proposed fractional Maxwell model can be used to simulate the start-up flow characteristics of viscoelastic elastomer in the orifice or gap of a shock absorber.