How to use separate map functions for different bodies?

[KunalGhoshGitHub]

Respected sir,

I am facing an issue while using this code. Actually, I want to use separate map functions for each of the separate bodies. Could you please help me with how to do it or refer me to any other resources for the same?

Thank you for your time and consideration.

Yours sincerely,
Kunal Ghosh

[weymouth]

What have you tried? You should be able to just define each body with is open map and then add them together...

[KunalGhoshGitHub]

Firstly, thank you for your time.

Actually, I was experimenting with one of the examples given (TwoD_cylinderVIV.jl).

I tried to define two bars (sdf_1 and sdf_2) but I am unable to figure out how to give two separate map functions to them.

Here is the modified code:

required to keep things global

let
# parameters
amp=π/4
ϵ=0.5
thk=2ϵ+√2
Re = 250; U = 1
p = 5; L = 2^p
radius = L/2

T = 4*radius    # VIV period

# initial condition FSI
p0=radius/3; v0=0.1*L; a0=0; t0=0

# motion function uses global var to adjust
posx(t) = p0 + (t-t0)*v0

function sdf_1(x,t)
    √sum(abs2,(2*L >= x[1] .> L) ? ((1.0*x[2] - L)) : x ) - thk/2
end

function sdf_2(x,t)
    √sum(abs2,(2*L <= x[1] .< 3*L) ? (x[1] .- (2.0*x[2])) : x ) - thk/2
end

sdf_list = [sdf_1,sdf_2]

function map(x,t)
    α = amp*cos(t*U/L); R = SA[cos(α) sin(α); -sin(α) cos(α)]
    R * (x - SA[3L-L*sin(0*t*U/L),4L])
end

body = AutoBody(map) do x,t  # signed distance function
        minimum(sdf_list) do SDF
            SDF(x,t)
        end
    end

# generate sim
sim = Simulation((10L,10L), (U,0), radius; ν=U*radius/Re, body=body)

# get start time
duration=10; step=0.1; t₀=round(sim_time(sim))

@time @gif for tᵢ in range(t₀,t₀+duration;step)

    # update until time tᵢ in the background
    t = sum(sim.flow.Δt[1:end-1])
    while t < tᵢ*sim.L/sim.U

        # measure body
        measure!(sim,t)

        # update flow
        mom_step!(sim.flow,sim.pois)
        
        Δt = sim.flow.Δt[end]
        p0 += Δt*v0 
        t0 = t; t += Δt
    end

    # plot vorticity
    @inside sim.flow.σ[I] = WaterLily.curl(3,I,sim.flow.u)*sim.L/sim.U
    flood(sim.flow.σ; shift=(-0.5,-0.5),clims=(-5,5))
    body_plot!(sim); plot!(title="tU/L $tᵢ")
    
    # print time step
    println("tU/L=",round(tᵢ,digits=4),", Δt=",round(sim.flow.Δt[end],digits=3))
end

end

[weymouth]

That's not a good example for applying two simple mappings. Take a look at #35. You just need to do something like:

using WaterLily,StaticArrays
function two_circles(n,m;Re=250,U=1)
    body1 = AutoBody((x,t)->√(x'*x) - m/8, map=(x,t)->x .- m/3 - SA_F32[t,0])
    body2 = AutoBody((x,t)->√(x'*x) - m/6, map=(x,t)->x .- 2m/3 + SA_F32[t,0])
    Simulation((n,m), (U,0), radius; ν=U*radius/Re, body=body1+body2)
end

I've created two maps with two different SDFs and maps. Then the body is just the sum of the two.

[weymouth]

I assume you figured it out...

[KunalGhoshGitHub]

Respected sir,

Yes, sir, I had figured it out. Thank you for the help.

Thank you for your time and consideration.

Yours sincerely,
Kunal Ghosh