Solution
= Solution
Take the downstream tissue <pressure> as gauge zero. The two transverse <momentum> fluxes cancel. The force of the fluid on the junction is axial and equals
$$
F=\left[A(p_{\rm up}-p_{\rm down})+\rho q(U-v\cos\alpha)\right]e_x,
$$
where $U=q/A$, $v=q/(2a)$ and the <pressure> difference is that in part (i).