The function estimates the Grashof Number, which describes the ability of a parcel of fluid warmer or colder than the surrounding fluid to rise against or fall with the attractive force of gravity (Gates 1980) . The Grashof Number is estimated as the ratio of a buoyant force times an inertial force to the square of a viscous force.

Grashof_number_Gates(T_a, T_g, beta, D, nu)

## Arguments

T_a

numeric Air temperature (C).

T_g

numeric Ground (surface) temperature (C).

beta

numeric coefficient of volumetric thermal expansion, beta = 3.67 x 10-3 C-1 in air and 41.9 x 10-4 C-1 in water.

D

numeric is characteristic dimension (e.g., body diameter) (m)

nu

numeric is the kinematic viscosity, the ratio of dynamic viscosity to density of the fluid (m2 s-1); can calculate from DRYAIR or WETAIR.

## Value

numeric Grashof number.

## References

Gates DM (1980). Biophysical Ecology. Springer-Verlag, New York, NY, USA.

Other biophysical models: Grashof_number(), Nusselt_from_Grashof(), Nusselt_from_Reynolds(), Nusselt_number(), Prandtl_number(), Qconduction_animal(), Qconduction_substrate(), Qconvection(), Qemitted_thermal_radiation(), Qevaporation(), Qmetabolism_from_mass_temp(), Qmetabolism_from_mass(), Qnet_Gates(), Qradiation_absorbed(), Qthermal_radiation_absorbed(), Reynolds_number(), T_sky(), Tb_CampbellNorman(), Tb_Gates2(), Tb_Gates(), Tb_butterfly(), Tb_grasshopper(), Tb_limpetBH(), Tb_limpet(), Tb_lizard_Fei(), Tb_lizard(), Tb_mussel(), Tb_salamander_humid(), Tb_snail(), Tbed_mussel(), Tsoil(), actual_vapor_pressure(), boundary_layer_resistance(), external_resistance_to_water_vapor_transfer(), free_or_forced_convection(), heat_transfer_coefficient_approximation(), heat_transfer_coefficient_simple(), heat_transfer_coefficient(), saturation_vapor_pressure(), saturation_water_vapor_pressure()
  Grashof_number_Gates(T_a   = 30,