Temperature Dependent Custom Fluid

I am attempting to use the Custom Hydraulic Fluid code in Simscape (custom_fluid.ssc) to make a variable temperature dependent fluid block (basically I need to run my model with both Skydrol LD-4 and Skydrol 5 so I wanted a switch the user can throw to use one or the other). To the custom_fluid.ssc code I added two inputs (temperature and fluid choice) and commented out the density, viscosity, and bulk modulus parameters. Then I added an equations block in which the curve-fits for the density, viscosity, and bulk modulus are included in an if block for the two fluids.

component(Propagation=source) mycustom_fluid
% Custom Hydraulic Fluid : 1.5 : fixed
% The block assigns fluid properties for all components assembled in 
% a particular loop. The loop detection is performed automatically and the
% block is considered as part of the loop if it is hydraulically connected
% to at least one of the loop components. If no Hydraulic Fluid block is
% connected to the loop, the default properties of the Custom Hydraulic 
% Fluid block are assigned.

inputs
    T = { 20, 'K' };        % T:left
    Fluid = { 1, '1' };     % Fld:left
end

parameters
%     density       = { 850   , 'kg/m^3' }; % Fluid density
%     viscosity_kin = { 18e-6 , 'm^2/s'  }; % Kinematic viscosity
%     bulk          = { 0.8e9 , 'Pa'     }; % Bulk modulus at atm. pressure and no gas
    alpha         = { 0.005 , '1'      }; % Relative amount of trapped air
    range_error   = { 2     , '1'      }; % Pressure below absolute zero
end

nodes
    G = foundation.hydraulic.hydraulic; % :right
end

function setup
%     if density <= 0
%         pm_error('simscape:GreaterThanZero', 'Fluid density');
%     end
%     if viscosity_kin <= 0
%         pm_error('simscape:GreaterThanZero', 'Kinematic viscosity');
%     end
%     if bulk <= 0
%         pm_error('simscape:GreaterThanZero', 'Bulk modulus at atm. pressure and no gas');
%     end
    if alpha < 0
        pm_error('simscape:GreaterThanOrEqual', 'Relative amount of trapped air','0');
    end
    if alpha == 0
        pm_warning('simscape:GreaterThan', 'In practice, the relative amount of trapped air', '0');
    end

%     G.density        = density;
%     G.viscosity_kin  = viscosity_kin;
%     G.bulk           = bulk;
    G.alpha          = alpha;
    G.range_error    = range_error;
end

equations

      if Fluid == 1 % Skydrol LD-4
          G.density        == -7.81300e-1*T + 1.00875e3;
          G.viscosity_kin  == 10^(8.90292e-10*T^4 - 5.41938e-7*T^3 + 1.31259e-4*T^2 - 1.84576e-2*T - 4.41859);
          G.bulk           == 2.22199e-3*T^5 - 1.47421*T^4 + 3.45233e2*T^3 - 2.04077e4*T^2 - 7.38360e6*T + 1.70081e9;
      else % Skydrol 5
          G.density        == -7.84600e-1*T + 0.99283e3;
          G.viscosity_kin  == 10^(0.11983e-10*T^4 - 7.12442e-7*T^3 + 1.64085e-4*T^2 - 2.07875e-2*T - 4.46965);
          G.bulk           == 0.24826e-3*T^5 - 0.13982*T^4 + 0.07082e2*T^3 - 1.77240e4*T^2 - 8.48723e6*T + 1.62466e9;        
      end

end
end

The curve-fits are taken from the data that Matlab includes for the two fluids in the Hydraulic Fluid block.

When I attempt to build this block (ssc_build) I get the following error...

Failed to generate 'CustomOrificeLib_lib'

Caused by: Error using ne_updatelibraryitem>lBuild (line 35) Source element has failed to resolve all shared data.

I'm fairly new to making my own blocks so I wouldn't be surprised if this was a small/obvious error, but I can't find help through other searches so I hoping my problem can be discussed here.

Thanks for any help you can offer.

Dan

Answer 1

[Aljen]

I got this message also when creating a Source for my custom domain. It turns out that it was linked to the domain parameters. It appears you need to define / mention all of them in the setup function. I am not sure how you can make sure that some are not changed w.r.t. the domain value, maybe with hidden parameters?

Answer 2

[Thomas LE DIOURON]

A component with variables fluids properties dependent on a variable temperature would be helpfull. I've tried with another way in Matlab R2016b. This code compiles but it fails during execution with the following error: "The following equation doesn't reference any variables or outputs."

component(Propagation=source) variable_fluid
% Variable fluid
% 
% This block enables to set variable density, kinematic viscosity and bulk moduluse
% for any kind of fluid.

parameters
    alpha         = { 0.005 , '1'      }; % Relative amount of trapped air
    range_error   = { 2     , '1'      }; % Pressure below absolute zero
end

nodes
    A = foundation.hydraulic.hydraulic; % :right
end

inputs
    density       = { 850   , 'kg/m^3' }; % Fluid density
    viscosity_kin = { 18e-6 , 'm^2/s'  }; % Kinematic viscosity
    bulk          = { 0.8e9 , 'Pa'     }; % Bulk modulus at atm. pressure and no gas
end

function setup
    if alpha < 0
        pm_error('simscape:GreaterThanOrEqual', 'Relative amount of trapped air','0');
    end
    if alpha == 0
        pm_warning('simscape:GreaterThan', 'In practice, the relative amount of trapped air', '0');
    end

      A.alpha          = alpha;
      A.range_error    = range_error;
  end

equations
    A.density        == density;
    A.viscosity_kin  == viscosity_kin;
    A.bulk           == bulk; 
end

end

Answer 3

[Tumelo Motlhanka]

Viscosity is a measure of how easily a fluid flow such as water. Thabo wants to investigate how viscosity of water varies with temperature which can be determined by the following correlation: Using MATLAB, create a table for Thabo that shows the viscosity of water as a function of temperature in the range of 0° C (273.15 K) to 100° C (373.15 K) in increments of 5° C. Also, create a graph showing the value of viscosity as a function of temperature.