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It is well known that, under plastic deformation, dislocations are not only created but also move through the crystal, and their mobility is impeded by their interaction with the crystal structure. At high stress and temperature, this &#8220;drag&#8222; is dominated by phonon wind, i.e., phonons scattering off dislocations. Employing the semi-isotropic approach discussed in detail in a previous paper (<i>J. Phys. Chem. Solids</i> <b>2019</b>, <i>124</i>, 24&#8211;35), we discuss here the approximate functional dependence of dislocation drag <i>B</i> on dislocation velocity in various regimes between a few percent of transverse sound speed <inline-formula> <math display="inline"> <semantics> <msub> <mi>c</mi> <mi mathvariant="normal">T</mi> </msub> </semantics> </math> </inline-formula> and <inline-formula> <math display="inline"> <semantics> <msub> <mi>c</mi> <mi mathvariant="normal">T</mi> </msub> </semantics> </math> </inline-formula> (where <inline-formula> <math display="inline"> <semantics> <msub> <mi>c</mi> <mi mathvariant="normal">T</mi> </msub> </semantics> </math> </inline-formula> is the effective average transverse sound speed of the polycrystal). In doing so, we find an effective functional form for dislocation drag <inline-formula> <math display="inline"> <semantics> <mrow> <mi>B</mi> <mo>(</mo> <mi>v</mi> <mo>)</mo> </mrow> </semantics> </math> </inline-formula> for different slip systems and dislocation characters at fixed (room) temperature and low pressure.