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-- Copyright (c) 2001 Mentor Graphics Corporation
--
-- This model is a component of the Mentor Graphics VHDL-AMS educational open 
-- source model library, and is covered by this license agreement. This model,
-- including any updates, modifications, revisions, copies, and documentation 
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-- THIS MODEL IS LICENSED TO YOU "AS IS" AND WITH NO WARRANTIES, EXPRESS OR 
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-- File       : constant_volume.vhd
-- Author     : Mentor Graphics
-- Created    : 2001-06-16
-- Last update: 2003-05-13
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-- Description: Constant Volume Fluid Chamber (hydraulic compliance)
-------------------------------------------------------------------------------
-- Revisions  :
-- Date        Version     Author              Description
-- 2001-06-16  1.0         Mentor Graphics     Created
-- 2002-05-21  1.1         Mentor Graphics     Updated std format
-------------------------------------------------------------------------------
--
--      ...Model Summary
--
-- The Constant Volume Fluid Chamber models the characteristics of hydraulic
-- compliance. The pressure used is that present at the hydraulic (FLUIDIC)
-- port. The polarity is consistant with the general convention where
-- the value is positive when the hydraulic "flow" is from port to
-- FLUIDIC_REF. The flow rate into the chamber is a function of the rate
-- the fluid compressibility due to change in pressure.
--
-- 
-- ...Netlist Example
--
-- This netlist example illustrates a typical application where the
-- volume model is used to simulate a fixed physical volume of fluid present
-- at a particular node in the system.
--
--  Volume_cavity: entity work.constant_volume (internal)
--              generic map (vol => 80.0e-6,
--                           bulk_modulus => 1.0e9
--                              )
--              port map (port1=> pr_spool);
-------------------------------------------------------------------------------

library IEEE;
use IEEE.MATH_REAL.all;
use IEEE.fluidic_systems.all;

entity constant_volume is
  generic (vol : volume;             -- Physical volume of chamber [m**3]
           bulk_modulus : pressure := 1.0e9); -- Fluid bulk modulus [N/m**2]
  port (terminal port1  : fluidic);
end entity constant_volume;
-- ...Model Characteristics
--
-- The flow rate into the chamber through port1 is modeled using the
-- following equation(s):
--
-- flow = d(vol_fluid)/dt
--      where
--      vol_fluid = instantaneous (effective) volume of fluid
--                = vol + (vol * pressure / bulk_modulus)

architecture behavioral of constant_volume is

  quantity p across flow through port1 to fluidic_ref;
  quantity vol_fluid : real := vol;

begin

  flow == vol_fluid'dot;
  vol_fluid == vol * (1.0 + p/bulk_modulus);

end architecture behavioral;
-------------------------------------------------------------------------------
-- Copyright (c) 2001 Mentor Graphics Corporation
-------------------------------------------------------------------------------