Table 1.

Force due to pressure gradient [Massoudi and Rao 2001 [47])]

Author	Pressure Term
Tchen, 1947	$\frac{4\pi a^3}{3}{\rho }_{\text{f}}\left(\frac{\partial {\text{v}}_p}{\partial t}+{\text{v}}_p\frac{\partial {\text{v}}_p}{\partial \text{x}}\right)$
Corrsin and Lumley, 1956	$\frac{4\pi a^3}{3}{\rho }_{\text{f}}\left(\frac{\partial {\mathbf{v}}_p}{\partial t}+(\mathbf{grad}{\mathbf{v}}_p){\mathbf{v}}_p-\nu {\nabla }^2{\mathbf{v}}_p\right)$
Buevich, 1966	$\frac{4\pi a^3}{3}{\rho }_{\text{f}}\left(\frac{\partial {\mathbf{v}}_p}{\partial t}+(\mathbf{grad}{\mathbf{v}}_p){\mathbf{v}}_f\right)$
Soo, 1975, 1976	0
Maxey and Riley, 1983	${\frac{4\pi a^3}{3}{\rho }_{\text{f}}\left(\frac{\partial {\mathbf{v}}_p}{\partial t}+(\mathbf{grad}{\mathbf{v}}_p){\mathbf{v}}_p\right)|}_{\mathbf{x}=\mathbf{y}(\mathbf{t})}$