A quantification of hydrodynamical effects on protoplanetary dust growth
A quantification of hydrodynamical effects on protoplanetary dust growth
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DOI：
10.1051/0004-6361/201321587
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发表时间：
2013-11
影响因子：
6.5
通讯作者：
E. Sellentin;J. Ramsey;F. Windmark;C. Dullemond
中科院分区：
文献类型：
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作者：
E. Sellentin;J. Ramsey;F. Windmark;C. Dullemond
上下文尘埃粒子在原行星盘中的生长过程可以通过数值尘埃凝聚程序来模拟。在这种方法中，控制尘埃生长过程的物理效应往往必须以参数化的形式实现。由于缺乏这些参数化，现有的粉尘凝聚的研究忽略了流体动力气流对晶粒生长的影响，即使人们经常认为，流动可能会显着贡献积极或消极的生长过程。目标。我们打算定性地描述影响小颗粒清扫的因素下流体动力学效应，然后通过量化这些效应的灰尘颗粒的生长，使它们可以被参数化，并在灰尘凝聚代码中实现。方法.使用一个简单的模型的流量，我们数值积分的小尘埃颗粒的轨迹在磁盘气体围绕原微行星，采样一个大的参数空间在原微行星半径，逆风速度，尘埃停止时间。结果气体流使大多数粒子偏离原微行星，使得其有效碰撞横截面减小，因此质量吸积速率减小。然而，气流也降低了小尘埃颗粒对原行星体的撞击速度。这可能有利于其生长，因为已知大的冲击速度会导致侵蚀。我们还证明了为什么这样的气流不返回碰撞碎片的表面的原星子。结论.我们预测，围绕原微行星的层流流体动力学流动将对其生长产生重要影响。然而，我们不能轻易地预测哪一个结果，即碰撞速度的减小或后掠截面的减小，将更重要。因此，我们提供了参数化准备实施到粉尘凝结代码。
Context. The growth process of dust particles in protoplanetary disks can be modeled via numerical dust coagulation codes. In this approach, physical e ects that dominate the dust growth process often must be implemented in a parameterized form. Due to a lack of these parameterizations, existing studies of dust coagulation have ignored the e ects a hydrodynamical gas flow can have on grain growth, even though it is often argued that the flow could significantly contribute either positively or negatively to the growth process. Aims. We intend to qualitatively describe the factors a ecting small particle sweep-up under hydrodynamical e ects, followed by a quantification of these e ects on the growth of dust particles, such that they can be parameterized and implemented in a dust coagulation code. Methods. Using a simple model for the flow, we numerically integrate the trajectories of small dust particles in disk gas around a proto-planetesimal, sampling a large parameter space in proto-planetesimal radii, headwind velocities, and dust stopping times. Results. The gas flow deflects most particles away from the proto-planetesimal, such that its e ective collisional cross section, and therefore the mass accretion rate, is reduced. The gas flow however also reduces the impact velocity of small dust particles onto a protoplanetesimal. This can be beneficial for its growth, since large impact velocities are known to lead to erosion. We also demonstrate why such a gas flow does not return collisional debris to the surface of a proto-planetesimal. Conclusions. We predict that a laminar hydrodynamical flow around a proto-planetesimal will have a significant e ect on its growth. However, we cannot easily predict which result, the reduction of the impact velocity or the sweep-up cross section, will be more important. Therefore, we provide parameterizations ready for implementation into a dust coagulation code.