lately i try to simulate flume in Nays2dh, i want ask Why is the flow velocity at the inner curve of the meandering river higher? Shouldn’t the velocity at the outer curve be higher due to centrifugal force? thankyou
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For a flat or nearly flat-bedded meander bend, the result you see if correct. Yours is common misconception. Here’s how to thing about it. As the water moves through the bend, it want to go straight, so you have to apply a force to make it go around the bend. The force is developed by the water piling up on the outer bank until the cross-stream water-surface slope is great enough to drive a pressure force the moves the flow around the bend. This is the well-known cross-stream surface slope found in river bends, with so-called super-elevation on the outer bank. But because the hydrostatic forces associated with water-surface slopes are coupled through the water-surface elevation, the increasing lateral water surface slope produces a relatively flat streamwise slope near the outer bank and a relatively steep streamwise slope near the inner bank, so the flow near the inner bank accelerates along the inner bank in response to that streamwise slope (in the absence of any topography). Thus, high velocities are found near the inner bank at the bend apex. Get it?
Thank you for your answer. I have a follow-up question. so is this condition normal? If not, how can we fix the calculation conditions so that the simulation results can match reality? namely the speed outside the corner is higher.
Thank you for your answer. I have a follow-up question. how to set the calculation conditions so that the simulation results can match reality? namely the speed outside the corner is higher.
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For a flat or nearly flat-bedded meander bend, the result you see if correct. Yours is common misconception. Here’s how to thing about it. As the water moves through the bend, it want to go straight, so you have to apply a force to make it go around the bend. The force is developed by the water piling up on the outer bank until the cross-stream water-surface slope is great enough to drive a pressure force the moves the flow around the bend. This is the well-known cross-stream surface slope found in river bends, with so-called super-elevation on the outer bank. But because the hydrostatic forces associated with water-surface slopes are coupled through the water-surface elevation, the increasing lateral water surface slope produces a relatively flat streamwise slope near the outer bank and a relatively steep streamwise slope near the inner bank, so the flow near the inner bank accelerates along the inner bank in response to that streamwise slope (in the absence of any topography). Thus, high velocities are found near the inner bank at the bend apex. Get it?
Thank you for your answer. I have a follow-up question. so is this condition normal? If not, how can we fix the calculation conditions so that the simulation results can match reality? namely the speed outside the corner is higher.
Thank you for your answer. I have a follow-up question. how to set the calculation conditions so that the simulation results can match reality? namely the speed outside the corner is higher.
3d model