  Radiative turbulent mixing layers (TMLs) are ubiquitous in astrophysical
environments, e.g., the circumgalactic medium (CGM), and are triggered by the
shear velocity at interfaces between different gas phases. To understand the
shear velocity dependence of TMLs, we perform a set of 3D hydrodynamic
simulations with an emphasis on the TML properties at high Mach numbers
$\mathcal{M}$. Since the shear velocity in mixing regions is limited by the
local sound speed of mixed gas, high-Mach number TMLs develop into a two-zone
structure: a Mach number-independent mixing zone traced by significant cooling
and mixing, plus a turbulent zone with large velocity dispersions which expands
with greater $\mathcal{M}$. Low-Mach number TMLs do not have distinguishable
mixing and turbulent zones. The radiative cooling of TMLs at low and high Mach
numbers is predominantly balanced by enthalpy consumption and turbulent
dissipation respectively. Both the TML surface brightness and column densities
of intermediate-temperature ions (e.g., O VI) scale as
$\propto\mathcal{M}^{0.5}$ at $\mathcal{M} \lesssim 1$, but reach saturation
($\propto \mathcal{M}^0$) at $\mathcal{M} \gtrsim 1$. Inflow velocities and hot
gas entrainment into TMLs are substantially suppressed at high Mach numbers,
and strong turbulent dissipation drives the evaporation of cold gas. This is in
contrast to low-Mach number TMLs where the inflow velocities and hot gas
entrainment are enhanced with greater $\mathcal{M}$, and cold gas mass
increases due to the condensation of entrained hot gas.
