- #1
PickledCucumber
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This is not really homework but an engineering problem nonetheless.
1. I have a venturi injector sucking in liquid (by all means and purposes identical to water) and injecting into a pressurized water line. A straight tube is inserted into the container of liquid (below the liquid surface) and connected to the throat of the injector. The container is open to the atmosphere. I would like to know if suction is possible. If so, what is the pressure difference at the throat of the injector and suction rate? Assume incompressible & irrotational flow, rigid pipe and neglect friction.
Givens:
##P_1=344.7 kPa##
##\rho=1000 kg/m^3 ##
##Q=0.05 LPM##
##g=9.81 m/s^2##
##d_1=0.0635 m##
##d_2=0.0125 m##
##d_4=0.05 m##
##h_2=2 m##
##h_3=0 m##
##h_4=0.5 m##
Relevant equations:
##Q=A*V##
## P_1/\rho + V_1^2/2 + gh_1=P_2/\rho + V_2^2/2 + gh_2 ##
I would analyze points 4 and 3 first. Then I would analyze points 3 and 2 to determine the pressure difference which will help me determine suction. However, I am unsure if my approach to the bernoullis balance is correct.
there are two variations I have looked into:
method 1: ##\frac{1}{\rho} \frac{dP_3}{dt}+ \frac{(\frac{dV_3}{dt})^2}{2} + gh_3=\frac{P_4}{\rho} + \frac{V_4^2}{2} + g \frac{dh_4}{dt}##
or
method 2: can we look at the change of pressure and velocity with respect to change in height rather than change in time.
Going with method 1:
I assume that h4 will decrease over time. I then also assumed the velocity and pressure are both dependent on each other and will vary over time as height decreases between h4 and h3
##\frac{dP_3}{dt}=\rho(g \frac{dh_4}{dt}- \frac{(\frac{dV_3}{dt})^2}{2})##
Now I am unsure what my time limits are when integrating.
Is my current approach reasonable? Is there an transient unsteady bernoullis balance that should be applied here instead? I have also been reading on the unsteady bernoullis equation derived from eulers equation.
1. I have a venturi injector sucking in liquid (by all means and purposes identical to water) and injecting into a pressurized water line. A straight tube is inserted into the container of liquid (below the liquid surface) and connected to the throat of the injector. The container is open to the atmosphere. I would like to know if suction is possible. If so, what is the pressure difference at the throat of the injector and suction rate? Assume incompressible & irrotational flow, rigid pipe and neglect friction.
Givens:
##P_1=344.7 kPa##
##\rho=1000 kg/m^3 ##
##Q=0.05 LPM##
##g=9.81 m/s^2##
##d_1=0.0635 m##
##d_2=0.0125 m##
##d_4=0.05 m##
##h_2=2 m##
##h_3=0 m##
##h_4=0.5 m##
Relevant equations:
##Q=A*V##
## P_1/\rho + V_1^2/2 + gh_1=P_2/\rho + V_2^2/2 + gh_2 ##
The Attempt at a Solution
I would analyze points 4 and 3 first. Then I would analyze points 3 and 2 to determine the pressure difference which will help me determine suction. However, I am unsure if my approach to the bernoullis balance is correct.
there are two variations I have looked into:
method 1: ##\frac{1}{\rho} \frac{dP_3}{dt}+ \frac{(\frac{dV_3}{dt})^2}{2} + gh_3=\frac{P_4}{\rho} + \frac{V_4^2}{2} + g \frac{dh_4}{dt}##
or
method 2: can we look at the change of pressure and velocity with respect to change in height rather than change in time.
Going with method 1:
I assume that h4 will decrease over time. I then also assumed the velocity and pressure are both dependent on each other and will vary over time as height decreases between h4 and h3
##\frac{dP_3}{dt}=\rho(g \frac{dh_4}{dt}- \frac{(\frac{dV_3}{dt})^2}{2})##
Now I am unsure what my time limits are when integrating.
Is my current approach reasonable? Is there an transient unsteady bernoullis balance that should be applied here instead? I have also been reading on the unsteady bernoullis equation derived from eulers equation.