Laminar and Turbulent Flow

Laminar and Turbulent Flow

1. Virtual model

   • 1. Horizontally arranged glass tube (10 mm diameter)
     • Used to study the movement of water
   • 2. Pressure tank
   • 3. A container dye solution
   • 4. Site of water discharge
     • Used to measure water flow
   • 5. A valve
   • 6. A control valve
     • Used to regulate the flow
   • 7. Piezometers
     • Used to determine the head losses
   • Cronometer
   • Measuring tank

2. Physical Process Description

   • Numerous experimental studies have established that fluid movement can occur either in the laminar or turbulent modes.
     • The turbulent mode is observed at considerable velocities and is characterized by intense mixing of fluid particles, which causes the pulsation of velocities and pressure
     • Laminar mode is observed at low velocities. fluid movement in the laminar mode is jet; there is no mixing of fluid particles.
       • The average flow velocity at which a change occurs in the mode of motion of a fluid is called critical Vcr, which depends on the type of fluid, characterized by dynamic viscosity ,density and the diameter of the pipeline.
         • The critical Reynolds number is a criterion that allows to judge the mode of movement of the fluid in a tube with a round cross-section, working full section.
           • If the Reynolds number is less than the critical one, then the fluid observed is in a stable laminar mode.
           • Formula # 2: Reynolds number
             • The v in the formula is called kinematic coefficient of viscosity of a fluid, and has m^2/s dimension.
           • Formula #1: Critical Reynolds number
           • If the Reynolds number is more than the critical one, then the fluid observed is in a turbulent mode.
           • Knowledge of the mode of motion of the fluid is necessary for the correct estimation of head losses in hydraulic calculations.
           • By using this graph, the magnitude of the critical velocity Vcr can be determined, and through it ‒ the critical Reynolds number by the formula #1

3. Laboratory Work Objectives

   • 1. To be convinced on experience by coloring of a stream of water in a glass pipe in existence of laminar and turbulent modes
     • 2. Calculate by experimental data of the Reynolds number in the laminar and turbulent modes and compare them with the critical one
       • 3. Plot the lgh1=f(lg v) graph, determine the critical velocity (Vcr) and calculate the critical Reynolds number
         • 4. Confirm that in the laminar mode the head loss along the length h1 is proportional to the average velocity in the first degree, and in the turbulent mode ‒ degree

4. The Order of the Work and the Processing of Experimental Data

   • 1. Open the water supply valve on the supply pipe and fill the pressure tank with water so that the overflow device works
     • 2. Open a slightly regulating valve on the glass tube so that the velocity of the water in it is small
       • 3. Open the tap on the container with the dye and turn on the flow of the dye solution into the glass tube
         • 4. Measure the flow of water Q
           • 5. Increase the velocity of water movement in the glass tube by opening the control valve, but in such a way that the colored trickle of fluid is maintained
             • 8. With a further increase in the opening of the control valve, create a turbulent mode in the glass tube.
               • Repeat steps 3 and 4 for the turbulent flow.
                 • 9. Do ten similar experiments, increasing the opening of the control valve in the range from 0 to 100% in each experiment so that 4–5 measurements were performed in a laminar mode, and 5–6 in a turbulent one.
                   • 10. Fill tables 1 and 2. Perform all calculations.
                     • 11. Build the lg h1= f(lg Vcr) graph. Determine the critical velocity Vcr and the Reynolds critical number, degrees mL, mT and coefficients BL and BT.
                       • 12. Give a conclusion based on the experiment's results.
                       • Reynolds critical number

5. Integrantes

   • Jesús David Claros
   • Nicolas Plaza
   • Fabian Salazar
   • Mateo Ruiz
   • Camila Carcache

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