Fluid Circuit Simulator

Click “Clear Diagram,” then use “Add Node” to place nodes. To try a ready-made circuit, click “Branching Example.”
Choose “Connect Channel,” drag from the start node along the desired path, and release over the end node. To add parallel channels between the same nodes, draw each along a separate path.
To remove an unconnected node, click it in “Select / Move” or “Connect Channel” mode, then click “Delete Selection.” In “Connect Channel” mode, click to select or drag to draw a channel.
In “Select / Move” mode, click a channel and choose its cross-section under “Selected Element.” Enter the width and height for a rectangle or the radius for a circle. Enter all dimensions, including length, in µm. The entered length is used to calculate resistance.
Use “Set Inlet” and “Set Outlet” to assign boundary nodes. Enter the inlet-to-outlet pressure difference and the dynamic viscosity. Set the outlet pressure as needed. Fluid density is used only to calculate the Reynolds number.
Use “Boundary Conditions and Fluid” to change units throughout the simulator. Pressure units are kPa, mmHg, mmH₂O, and PSI. Flow units are µL/min, mL/min, µL/s, and mL/s. Entered pressures are converted automatically.
The diagram shows node pressures and flow directions. “Channel Dimensions” lists shapes and dimensions. “Results” lists flow rate, pressure drop, resistance, and Reynolds number for each channel. Resistance equations and model assumptions appear below the results.

Channel Dimensions

Channel (connection order)	Cross-section	Width [µm]	Height [µm]	Radius [µm]	Length [µm]

Results

Channel (connection order)	Flow rate [µL/min]	Pressure drop [kPa]	Resistance [kPa/(µL/min)]	Re

Each channel uses the resistance equation for its rectangular or circular cross-section. The model assumes steady, fully developed laminar flow of an incompressible Newtonian fluid and omits local losses at junctions. The signs of flow rate and pressure drop follow the connection order shown in the table.

Rectangular cross-section R = 12μL / {ab³ [1 − (192b/π⁵a) Σ tanh(nπa/2b)/n⁵]}. Here, a is the larger of the width and height, and b is the smaller. The series is evaluated for odd n = 1, 3, …, 99.

Circular cross-section R = 8μL/(πr⁴) (Hagen–Poiseuille equation). Here, r is the radius.

μ is the dynamic viscosity and L is the channel length. Resistance R is calculated in SI units [Pa·s/m³], and flow rate follows from Q = ΔP/R.