bronbron85
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- Dec 22, 2015
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A horizontal temperature gradient, ∂T/∂x, generated through differential heating can drive an exchange flow whose layer-averaged motion, u , is determined by the momentum equation:
∂u/∂t ~ g a ∂T/∂x H (Equation 1)
where a is the thermal expansion coefficient of water, g is the acceleration due to gravity, and H is the layer depth.
The layer averaged momentum increases until a balance is reached between the rate of thermal energy input and the loss of thermal energy via advection, i.e. at steady state:
∂T/∂t ~ u ∂T/∂x (Equation 2)
Combining equations 1 and 2, and approximating ∂T/∂x by ΔT/L leads to the following estimate for the layer velocity once steady-state is reached.
u ~ (g a ΔT H)^1/2 (Equation 3)
Can someone please explain how to get from Equations 1 and 2 to Equation 3? Please explain all the steps. I do not know anything about solving differential equations but would like to learn. I have probably put too much detail into the science here (I hope this doesn't distract people). It is actually the mathematics I am struggling to understand.
∂u/∂t ~ g a ∂T/∂x H (Equation 1)
where a is the thermal expansion coefficient of water, g is the acceleration due to gravity, and H is the layer depth.
The layer averaged momentum increases until a balance is reached between the rate of thermal energy input and the loss of thermal energy via advection, i.e. at steady state:
∂T/∂t ~ u ∂T/∂x (Equation 2)
Combining equations 1 and 2, and approximating ∂T/∂x by ΔT/L leads to the following estimate for the layer velocity once steady-state is reached.
u ~ (g a ΔT H)^1/2 (Equation 3)
Can someone please explain how to get from Equations 1 and 2 to Equation 3? Please explain all the steps. I do not know anything about solving differential equations but would like to learn. I have probably put too much detail into the science here (I hope this doesn't distract people). It is actually the mathematics I am struggling to understand.
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