Hello, I am investigating a phenomenon known as "Blood reflux" and I am interested in the Hydraulic Principles I need to understand to solve a problem related to this. Here is the problem: PROBLEM: - A 20 gauge plastic tube is inserted into a vein with a 6mm diameter. The end of this plastic tube is oriented in the direction of flow. This 20 gauge plastic tube is flushed clear of blood and clamped 10cm from the tip residing in the 6mm vein. This effectively creates a tube closed on one end inserted into a flowing liquid. The clamped tube (assuming clamping is effective) will fill with blood some time later - this is known as reflux. QUESTION: - What principles of hydraulic theory effect this situation? I would like to learn about these principles and work to understand the mechanisms that are involved. Hopefully this will lead me to understand the circumstances that can cause this and then work to predict and prevent them. Thanks.