tag:blogger.com,1999:blog-6789188.post5014234553940818912..comments2024-03-27T17:15:37.606-04:00Comments on Triablogue: HydrodynamicsRyanhttp://www.blogger.com/profile/17809283662428917799noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-6789188.post-32234778116268111062019-10-18T12:32:07.260-04:002019-10-18T12:32:07.260-04:00"Rivers can aggrade (fill in) or incise (cut ..."Rivers can aggrade (fill in) or incise (cut down) over time depending on the balance of sediment they receive to the power of the flow to move it. A river with a balance between the two will just shunt sediment on downstream...The transport capacity of the flow keeps the channel open. Most channels are adjusted (in the width/depth) to carry what is known as the “bankfull” flow, which tends to be close to the annual high flood."<br /><br />Interestingly, this might be (sort of) similar to blood flow in the human body. Specifically resistance to blood flow. This is determined by something called Poiseuille's equation. The most pertinent parts of the equation are:<br /><br />1. <b>Viscosity</b> ("sediments" clogging the blood vessel or river). Resistance to blood flow is directly proportional to the viscosity (η) of the blood. For example, if viscosity increases, then resistance to blood flow increases.<br /><br />2. <b>Length</b> (of the blood vessel or river). Resistance to blood flow is directly proportional to the length (l) of the blood vessel. For example, if the blood vessel lengthens, then resistance to blood flow increases.<br /><br />3. <b>Radius</b> (of the blood vessel or river). Resistance to blood flow is inversely proportional to the 4th power of the radius (r^4) of the blood vessel. When the radius of a blood vessel decreases, its resistance increases. However, resistance doesn't increase in a linear fashion. Rather it's magnified to the 4th power. For example, if the radius of a blood vessel decreases by half, resistance doesn't increase two-fold but 16-fold. However, importantly, the main difference is, unlike blood vessels, rivers aren't typically fully enclosed like a tube. Instead rivers are more like a semi-circular tube. Hawkhttps://www.blogger.com/profile/01142879704651632453noreply@blogger.com