I’m trying to create a minimal model in Simscape to replicate the Venturi effect in a Simscape Gas model: Gas is flowing from point A to point B, and the cross-sectional area of the duct at point A is smaller than B; as a result, the static pressure at A must be lower than B (assuming negligible energy loss from A to B).
I tried two different setups to replicate this. First, I used a "Local Restriction (G)" block (with a fixed restriction area), which has this orifice structure built in. The flow is provided by a Flow Rate Source block, and I added a Flow Resistance block downstream to allow the pressure at the port B of the Local Restriction to vary. Here is a screenshot of the model:

I expect that at least for some combination of restriction area and flow rate, the pressure at the restriction, p_R, must be lower than port B. I tried running the simulation with different values of flow rate and restriction area, but p_R was always higher than pressure at B.
Next, I used two consecutive Pipe (G) elements: the first one with a smaller surface area and hydraulic diameter, and the second with larger values for both. The rest of the setup is similar:

Again, I expect the internal pressure of the Small Pipe to be lower than the internal pressure of the Big Pipe, but this was never the case. I ran the simulation for different values of pipe surface area and hydraulic diameter for the two pipes, and kept the pipe length, internal surface roughness, and the laminar friction constants low to reduce the pressure loss due to friction. I also tried reducing the dynamic viscosity in the Gas Properties block, and disabling/enabling gas compressibility in the pipes.

In both models, I kept the rest of the settings and parameters as default (e.g., perfect gas with properties of dry air, daessc solver, etc.). The models are attached.

Am I doing something wrong, or are there any limitations and theoretical assumptions in Simscape Gas that do not allow replicating this effect?

Thanks in advance!I’m trying to create a minimal model in Simscape to replicate the Venturi effect in a Simscape Gas model: Gas is flowing from point A to point B, and the cross-sectional area of the duct at point A is smaller than B; as a result, the static pressure at A must be lower than B (assuming negligible energy loss from A to B).
I tried two different setups to replicate this. First, I used a "Local Restriction (G)" block (with a fixed restriction area), which has this orifice structure built in. The flow is provided by a Flow Rate Source block, and I added a Flow Resistance block downstream to allow the pressure at the port B of the Local Restriction to vary. Here is a screenshot of the model:

I expect that at least for some combination of restriction area and flow rate, the pressure at the restriction, p_R, must be lower than port B. I tried running the simulation with different values of flow rate and restriction area, but p_R was always higher than pressure at B.
Next, I used two consecutive Pipe (G) elements: the first one with a smaller surface area and hydraulic diameter, and the second with larger values for both. The rest of the setup is similar:

Again, I expect the internal pressure of the Small Pipe to be lower than the internal pressure of the Big Pipe, but this was never the case. I ran the simulation for different values of pipe surface area and hydraulic diameter for the two pipes, and kept the pipe length, internal surface roughness, and the laminar friction constants low to reduce the pressure loss due to friction. I also tried reducing the dynamic viscosity in the Gas Properties block, and disabling/enabling gas compressibility in the pipes.

In both models, I kept the rest of the settings and parameters as default (e.g., perfect gas with properties of dry air, daessc solver, etc.). The models are attached.

Am I doing something wrong, or are there any limitations and theoretical assumptions in Simscape Gas that do not allow replicating this effect?

Thanks in advance! I’m trying to create a minimal model in Simscape to replicate the Venturi effect in a Simscape Gas model: Gas is flowing from point A to point B, and the cross-sectional area of the duct at point A is smaller than B; as a result, the static pressure at A must be lower than B (assuming negligible energy loss from A to B).
I tried two different setups to replicate this. First, I used a "Local Restriction (G)" block (with a fixed restriction area), which has this orifice structure built in. The flow is provided by a Flow Rate Source block, and I added a Flow Resistance block downstream to allow the pressure at the port B of the Local Restriction to vary. Here is a screenshot of the model:

I expect that at least for some combination of restriction area and flow rate, the pressure at the restriction, p_R, must be lower than port B. I tried running the simulation with different values of flow rate and restriction area, but p_R was always higher than pressure at B.
Next, I used two consecutive Pipe (G) elements: the first one with a smaller surface area and hydraulic diameter, and the second with larger values for both. The rest of the setup is similar:

Again, I expect the internal pressure of the Small Pipe to be lower than the internal pressure of the Big Pipe, but this was never the case. I ran the simulation for different values of pipe surface area and hydraulic diameter for the two pipes, and kept the pipe length, internal surface roughness, and the laminar friction constants low to reduce the pressure loss due to friction. I also tried reducing the dynamic viscosity in the Gas Properties block, and disabling/enabling gas compressibility in the pipes.

In both models, I kept the rest of the settings and parameters as default (e.g., perfect gas with properties of dry air, daessc solver, etc.). The models are attached.

Am I doing something wrong, or are there any limitations and theoretical assumptions in Simscape Gas that do not allow replicating this effect?

Thanks in advance! simscape, gas, fluid dynamics, simulation MATLAB Answers — New Questions

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