Added Valve component and minimum_volume feature to the DynamicVolume component

src/Hydraulic/IsothermalCompressible/IsothermalCompressible.jl

@@ -3,17 +3,17 @@ Library to model iso-thermal compressible liquid fluid flow
 """
 module IsothermalCompressible
 
-using ModelingToolkit, Symbolics
+using ModelingToolkit, Symbolics, IfElse
 using ...Blocks: RealInput, RealOutput
 using ...Mechanical.Translational: MechanicalPort
 
 @parameters t
 D = Differential(t)
 
-export HydraulicPort
+export HydraulicPort, HydraulicFluid
 include("utils.jl")
 
-export Source, InputSource, FixedVolume, Pipe
+export Source, InputSource, Cap, Pipe, FixedVolume, DynamicVolume
 include("components.jl")
 
 end

src/Hydraulic/IsothermalCompressible/components.jl

@@ -226,7 +226,7 @@ Pipe modeled with `N` segements which models the fully developed flow friction a
 end
 
 """
-    DynamicVolume(; p_int, x_int=0, area, dead_volume=0, direction=+1, name)
+    DynamicVolume(; p_int, x_int=0, area, dead_volume=0, direction=+1, minimum_volume=0, name)
 
 Volume with moving wall.  The `direction` argument aligns the mechanical port with the hydraulic port, useful when connecting two dynamic volumes together in oppsing directions to create an actuator.
 ```
@@ -242,17 +242,18 @@ dm ────►  dead volume  │  │ area
 ```
 
 # Parameters:
-- `p_int`: [Pa] initial pressure (set by `p_int` argument)
-- `x_int`: [m] initial position of the moving wall (set by the `x_int` argument)
-- `area`: [m^2] moving wall area (set by the `area` argument)
-- `dead_volume`: [m^3] perimeter of the pipe cross section (set by optional `perimeter` argument, needed only for non-circular pipes)
+- `p_int`: [Pa] initial pressure
+- `x_int`: [m] initial position of the moving wall
+- `area`: [m^2] moving wall area
+- `dead_volume`: [m^3] perimeter of the pipe cross section
+- `minimum_volume`: [m^3] if `x`*`area` <= `minimum_volume` then mass flow `dm` shuts off
 
 # Connectors:
 - `port`: hydraulic port
 - `flange`: mechanical translational port
 """
 @component function DynamicVolume(; p_int, x_int = 0, area, dead_volume = 0, direction = +1,
-                                  name)
+                                  minimum_volume = 0, name)
     @assert (direction == +1)||(direction == -1) "direction arument must be +/-1, found $direction"
 
     pars = @parameters begin
@@ -272,17 +273,62 @@ dm ────►  dead volume  │  │ area
         dx(t) = 0
         rho(t) = density(port, p_int)
         drho(t) = 0
+        vol(t) = dead_volume + area * x_int
+        p(t) = p_int
     end
 
-    # let -------------
-    vol = dead_volume + area * x
-
-    eqs = [D(x) ~ dx
+    eqs = [0 ~ IfElse.ifelse(vol >= minimum_volume, p - port.p, port.dm)
+           vol ~ dead_volume + area * x
+           D(x) ~ dx
            D(rho) ~ drho
            dx ~ flange.v * direction
-           rho ~ density(port, port.p)
+           rho ~ density(port, p)
            port.dm ~ drho * vol + rho * area * dx
-           flange.f ~ -port.p * area * direction]
+           flange.f ~ -p * area * direction] #TODO: update to dynamic pressure
 
-    ODESystem(eqs, t, vars, pars; name, systems)
+    ODESystem(eqs, t, vars, pars; name, systems, defaults = [flange.v => 0])
+end
+
+"""
+    Valve(; p_a_int, p_b_int, area_int, Cd, name)
+
+Valve with area input and discharge coefficient `Cd` defined by https://en.wikipedia.org/wiki/Discharge_coefficient
+
+# Parameters:
+- `p_a_int`: [Pa] initial pressure for `port_a`
+- `p_b_int`: [Pa] initial pressure for `port_b`
+- `area_int`: [m^2] initial valve opening
+- `Cd`: discharge coefficient 
+
+# Connectors:
+- `port_a`: hydraulic port
+- `port_b`: hydraulic port
+- `input`: real input setting the valve `area`.  Note: absolute value taken
+"""
+@component function Valve(; p_a_int, p_b_int, area_int, Cd, name)
+    pars = @parameters begin
+        p_a_int = p_a_int
+        p_b_int = p_b_int
+        area_int = area_int
+        Cd = Cd
+    end
+
+    systems = @named begin
+        port_a = HydraulicPort(; p_int = p_a_int)
+        port_b = HydraulicPort(; p_int = p_b_int)
+        input = RealInput()
+    end
+
+    vars = []
+
+    # let
+    ρ = (density(port_a, port_a.p) + density(port_b, port_b.p)) / 2
+    Δp = port_a.p - port_b.p
+    dm = port_a.dm
+    area = abs(input.u)
+
+    eqs = [sign(Δp) * dm ~ sqrt(2 * abs(Δp) * ρ / Cd) * area
+           0 ~ port_a.dm + port_b.dm]
+
+    ODESystem(eqs, t, vars, pars; name, systems, defaults = [input.u => area_int])
 end

test/Hydraulic/isothermal_compressible.jl

@@ -6,7 +6,9 @@ import ModelingToolkitStandardLibrary.Mechanical.Translational as T
 @parameters t
 D = Differential(t)
 
-function system(N; bulk_modulus, name)
+# ------------------------------------------------------------
+# Test fluid domain and Pipe
+function System(N; bulk_modulus, name)
     pars = @parameters begin bulk_modulus = bulk_modulus end
 
     systems = @named begin
@@ -32,9 +34,9 @@ function system(N; bulk_modulus, name)
     ODESystem(eqs, t, [], pars; name, systems)
 end
 
-@named sys1_2 = system(1; bulk_modulus = 2e9)
-@named sys1_1 = system(1; bulk_modulus = 1e9)
-@named sys5_1 = system(5; bulk_modulus = 1e9)
+@named sys1_2 = System(1; bulk_modulus = 2e9)
+@named sys1_1 = System(1; bulk_modulus = 1e9)
+@named sys5_1 = System(5; bulk_modulus = 1e9)
 
 NEWTON = NLNewton(check_div = false, always_new = true, max_iter = 100, relax = 4 // 10)
 
@@ -53,77 +55,97 @@ s5_1 = complete(sys5_1)
 # N=5 pipe is compressible, will pressurize more slowly
 @test sols[2][s1_1.vol.port.p][end] > sols[3][s5_1.vol.port.p][end]
 
-# using CairoMakie
-# fig = Figure()
-# ax = Axis(fig[1,1])
-# lines!(ax, sols[1].t, sols[1][s1_2.src.port.p]; label="sorce", color=:black)
-# # lines!(ax, sols[2].t, sols[2][s1_1.src.port.p])
-# scatterlines!(ax, sols[1].t, sols[1][s1_2.vol.port.p]; label="bulk=2e9")
-# scatterlines!(ax, sols[2].t, sols[2][s1_1.vol.port.p]; label="bulk=1e9")
-# scatterlines!(ax, sols[3].t, sols[3][s5_1.vol.port.p]; label="bulk=1e9, N=5")
-# Legend(fig[1,2], ax)
-# fig
-
-function system(; bulk_modulus, name)
-    pars = @parameters begin bulk_modulus = bulk_modulus end
+# ------------------------------------------------------------
+# Test the Valve 
+function System(; name)
+    pars = []
 
     systems = @named begin
-        fluid = IC.HydraulicFluid(; bulk_modulus)
-        stp = B.Step(; height = 10e5, offset = 0, start_time = 0.05, duration = Inf,
-                     smooth = 0.001)
-        src = IC.InputSource(; p_int = 0)
-        vol1 = IC.DynamicVolume(; p_int = 0, area = 0.01, direction = +1)
-        vol2 = IC.DynamicVolume(; p_int = 0, area = 0.01, direction = -1, x_int = 1.0)
-        mass = T.Mass(; m = 1000, s_0 = 0)
-        res = IC.PipeBase(; p_int = 0, area = 0.001, length = 50.0)
-        cap = IC.Cap(; p_int = 0)
+        fluid = IC.HydraulicFluid()
+        sink = IC.Source(; p = 10e5)
+        vol = IC.FixedVolume(; vol = 0.1, p_int = 100e5)
+        valve = IC.Valve(; p_a_int = 10e5, p_b_int = 100e5, area_int = 0, Cd = 1e6)
+        ramp = B.Ramp(; height = 1, duration = 0.001, offset = 0, start_time = 0.001,
+                      smooth = true)
     end
 
-    eqs = [connect(stp.output, src.input)
-           connect(fluid, src.port, cap.port)
-           connect(src.port, res.port_a)
-           connect(res.port_b, vol1.port)
-           connect(vol1.flange, mass.flange, vol2.flange)
-           connect(vol2.port, cap.port)]
+    eqs = [connect(fluid, sink.port)
+           connect(sink.port, valve.port_a)
+           connect(valve.port_b, vol.port)
+           connect(valve.input, ramp.output)]
 
     ODESystem(eqs, t, [], pars; name, systems)
 end
 
-@named sys1 = system(; bulk_modulus = 1e9)
-@named sys2 = system(; bulk_modulus = 2e9)
+@named valve_system = System()
+s = complete(valve_system)
+sys = structural_simplify(valve_system)
+prob = ODEProblem(sys, [], (0, 0.01))
+sol = solve(prob, ImplicitEuler(nlsolve = NEWTON); adaptive = false, dt = 1e-4,
+            initializealg = NoInit())
 
-syss = structural_simplify.([sys1, sys2])
-probs = [ODEProblem(sys, [], (0, 0.2)) for sys in syss];
-dt = 1e-4
-sols = [solve(prob, ImplicitEuler(nlsolve = NEWTON); adaptive = false, dt,
-              initializealg = NoInit()) for prob in probs];
-
-s1 = complete(sys1)
-s2 = complete(sys2)
-
-# less stiff will compress more
-@test maximum(sols[1][s1.mass.s]) > maximum(sols[2][s2.mass.s])
-
-# fig = Figure()
-# ax = Axis(fig[1,1])
-# lines!(ax, sols[1].t, sols[1][s1.src.port.p]; label="sorce", color=:black)
-# # lines!(ax, sols[2].t, sols[2][s1_1.src.port.p])
-# scatterlines!(ax, sols[1].t, sols[1][s1.vol1.port.p]; label="bulk=1e9")
-# scatterlines!(ax, sols[2].t, sols[2][s2.vol1.port.p]; label="bulk=2e9")
-# Legend(fig[1,2], ax)
-# fig
-
-# fig = Figure()
-# ax = Axis(fig[1,1])
-# scatterlines!(ax, sols[1].t, sols[1][s1.mass.s]; label="bulk=1e9")
-# scatterlines!(ax, sols[2].t, sols[2][s2.mass.s]; label="bulk=2e9")
-# Legend(fig[1,2], ax)
-# fig
-
-# fig = Figure()
-# ax = Axis(fig[1,1])
-# lines!(ax, sols[1].t, sols[1][s1.vol1.dx]; label="bulk=2e9")
-# lines!(ax, sols[1].t, sols[1][s1.vol2.dx]; label="bulk=2e9")
-# lines!(ax, sols[1].t, sols[1][s1.mass.v]; label="bulk=2e9")
-# Legend(fig[1,2], ax)
-# fig
+# the volume should discharge to 10bar
+@test sol[s.vol.port.p][end] ≈ 10e5
+
+# ------------------------------------------------------------
+# Test DynmaicVolume and minimum_volume feature
+function System(; name)
+    pars = []
+
+    # DynamicVolume values
+    area = 0.01
+    length = 0.1
+
+    systems = @named begin
+        fluid = IC.HydraulicFluid()
+        src1 = IC.InputSource(; p_int = 10e5)
+        src2 = IC.InputSource(; p_int = 10e5)
+
+        vol1 = IC.DynamicVolume(; p_int = 10e5, area, direction = +1, dead_volume = 2e-4,
+                                minimum_volume = 2e-4)
+        vol2 = IC.DynamicVolume(; p_int = 10e5, area, direction = -1, dead_volume = 2e-4,
+                                minimum_volume = 2e-4, x_int = length)
+
+        mass = T.Mass(; m = 100)
+
+        sin1 = B.Sine(; frequency = 0.5, amplitude = +1e5, offset = 10e5)
+        sin2 = B.Sine(; frequency = 0.5, amplitude = -1e5, offset = 10e5)
+    end
+
+    eqs = [connect(fluid, src1.port, src2.port)
+           connect(src1.port, vol1.port)
+           connect(src2.port, vol2.port)
+           connect(vol1.flange, mass.flange, vol2.flange)
+           connect(src1.input, sin1.output)
+           connect(src2.input, sin2.output)]
+
+    ODESystem(eqs, t, [], pars; name, systems)
+end
+
+@named min_vol_system = System()
+s = complete(min_vol_system)
+sys = structural_simplify(min_vol_system)
+prob = ODEProblem(sys, [], (0, 5.0))
+
+sol = solve(prob, ImplicitEuler(nlsolve = NEWTON); adaptive = false, dt = 1e-4,
+            initializealg = NoInit())
+
+# begin
+#     fig = Figure()
+
+#     ax = Axis(fig[1,1], ylabel="position [m]", xlabel="time [s]")
+#     lines!(ax, sol.t, sol[s.vol1.x]; label="vol1")
+#     lines!(ax, sol.t, sol[s.vol2.x]; label="vol2")
+
+#     ax = Axis(fig[2,1], ylabel="pressure [bar]", xlabel="time [s]")
+#     lines!(ax, sol.t, sol[s.vol1.port.p]/1e5; label="vol1")
+#     lines!(ax, sol.t, sol[s.vol2.port.p]/1e5; label="vol2")
+#     Legend(fig[2,2], ax)
+#     fig    
+# end
+
+# volume/mass should stop moving at opposite ends
+@test round(sol[s.vol1.x][1]; digits = 2) == 0.0
+@test round(sol[s.vol2.x][1]; digits = 2) == 0.1
+@test round(sol[s.vol1.x][end]; digits = 2) == 0.1
+@test round(sol[s.vol2.x][end]; digits = 2) == 0.0

test/runtests.jl

@@ -24,3 +24,6 @@ using SafeTestsets
 @safetestset "Mechanical Rotation" begin include("Mechanical/rotational.jl") end
 @safetestset "Mechanical Translation" begin include("Mechanical/translational.jl") end
 @safetestset "Multi-Domain" begin include("multi_domain.jl") end
+
+# Hydraulic
+@safetestset "Hydraulic IsothermalCompressible" begin include("Hydraulic/isothermal_compressible.jl") end