UWAVE

User subroutine to define wave kinematics for an Abaqus/Aqua analysis.

User subroutine UWAVE:

will be called at each load integration point for which an Abaqus/Aqua load is specified and a user-defined gravity wave is specified;
can be used to define the wave kinematics (fluid velocity and acceleration, dynamic pressure, vertical gradient of the dynamic pressure, and the instantaneous fluid surface elevation) as a function of time and space; and
for stochastic analysis, can be used to determine when during the analysis the current configuration should be retained as the intermediate configuration upon which the wave kinematics are based.

The following topics are discussed:

User subroutine interface
Variables to be defined
Variables passed in for information

User subroutine interface

      SUBROUTINE UWAVE(V,A,PDYN,DPDYNDZ,SURF,LPDYN
     1 LRECOMPUTE,LUPLOCAL,LUPGLOBAL,
     2 LSURF,NDIM,XCUR,XINTERMED,
     3 GRAV,DENSITY,ELEVB,ELEVS,
     4 SEED,NSPECTRUM,FREQWAMP,
     5 TIME,DTIME,NOEL,NPT,KSTEP,KINC)
C
      INCLUDE 'ABA_PARAM.INC'
C
      DIMENSION V(NDIM),A(NDIM),XCUR(NDIM),XINTERMED(NDIM),
     1 FREQWAMP(2,NSPECTRUM),TIME(2)


      user coding to define V, A, PDYN, DPDYNDZ, SURF
      and, if necessary, LUPGLOBAL and LUPLOCAL


      RETURN
      END

Variables to be defined

When LSURF=0
V(NDIM): The total fluid velocity at the current load integration location. This array is passed into UWAVE as the steady current velocity. The array should be updated as the sum of the steady current velocity and the velocity contribution from the user-defined wave theory.
A(NDIM): The fluid acceleration at the current load integration location.
PDYN: The dynamic pressure contribution to the total pressure. This variable is needed only for buoyancy loads. The total pressure at a location below the instantaneous surface elevation is the sum of the atmospheric pressure, the hydrostatic pressure measured to the mean fluid elevation, and the dynamic pressure. See Airy wave theory and Stokes wave theory for definitions of the dynamic pressure for Airy and Stokes waves, respectively.
DPDYNDZ: The gradient of the dynamic pressure in the vertical direction. This variable is needed only for buoyancy loads.

When LSURF=1
SURF: The vertical coordinate of the instantaneous fluid surface corresponding to the horizontal position of the load integration point (given in XCUR). If the current location of the load integration point is above the instantaneous surface elevation, no fluid loads will be applied.

Only in an analysis with stochastic wave kinematics based on an intermediate configuration
LUPLOCAL: Flag to determine if the intermediate configuration will be updated for this element. This flag can be set only when LRECOMPUTE=1. Return LUPLOCAL as 0 (default) to indicate that the intermediate configuration should not be updated. Return LUPLOCAL as 1 if the intermediate configuration should be updated for this element. The intermediate configuration is stored on an element-by-element basis. Therefore, all integration points for a given element will have their intermediate configuration updated if an update is requested at any one integration point on the element.
LUPGLOBAL: Flag to determine if the intermediate configuration will be updated for all elements. This flag can be set only when LRECOMPUTE=1. Return LUPGLOBAL as 0 (default) to indicate that the intermediate configuration should not be updated. Return LUPGLOBAL as 1 if the intermediate configuration should be updated for all elements with Abaqus/Aqua loads.

Variables passed in for information

LRECOMPUTE: For stochastic analysis LRECOMPUTE=1 indicates that an update to the intermediate configuration is permitted during this call to user subroutine UWAVE. The local and global update flags must be set accordingly. If the intermediate configuration is to be updated, the local update flag LUPLOCAL or the global update flag LUPGLOBAL must be set to 1. When LRECOMPUTE=1 and the intermediate configuration needs to be updated, the user subroutine should recompute all wave kinematics information based on the new intermediate configuration. For nonstochastic analysis this flag is always set to 0.
LPDYN: LPDYN=1 indicates that only the dynamic pressure and its gradient need to be calculated (i.e., buoyancy loads). LPDYN=0 indicates that only the fluid velocity and acceleration need to be calculated (i.e., drag or inertia loads).
LSURF: LSURF=1 indicates that subroutine UWAVE only needs to return the instantaneous fluid surface elevation. When LSURF=1, no velocity, acceleration, or dynamic pressure needs to be calculated. LSURF=0 indicates that the instantaneous fluid surface elevation SURF is not needed.
NDIM: Two or three, indicating that the analysis is in two or three dimensions. The vertical direction is the global y-direction in two-dimensional analysis and the global z-direction in three-dimensional analysis.
XCUR(NDIM): An array containing the current coordinates of the load integration point.
XINTERMED(NDIM): An array containing the intermediate configuration coordinates of the load integration point. For nonstochastic analysis this array is not used. In a stochastic analysis the wave field is based upon this configuration. At the beginning of each load increment the LRECOMPUTE flag is set to 1 to prompt you for update action. If the intermediate configuration should be replaced by the current configuration, the flag LUPLOCAL should be set to 1 to update the intermediate configuration for this element only or the flag LUPGLOBAL should be set to 1 to update the intermediate configuration for all elements that have Abaqus/Aqua loading. At the beginning of the analysis the intermediate configuration is the reference configuration.
GRAV: The user-specified gravitational constant in the fluid variable definition.
DENSITY: The user-specified fluid mass density in the fluid variable definition.
ELEVB: The user-specified elevation of the seabed in the fluid variable definition.
ELEVS: The user-specified elevation of the still fluid level in the fluid variable definition.
SEED: For stochastic analysis the user-specified random number seed in the gravity wave definition.
NSPECTRUM: For stochastic analysis the number of user-specified frequency versus wave amplitude pairs in the gravity wave definition, used to define the wave spectrum.
FREQWAMP(1,NSPECTRUM): For stochastic analysis the frequency values used to define the wave spectrum.
FREQWAMP(2,NSPECTRUM): For stochastic analysis the wave amplitude values used to define the wave spectrum.
TIME(1): Value of step time at the end of the current increment.
TIME(2): Value of total time at the end of the current increment.
DTIME: Time increment.
NOEL: Element number.
NPT: Load integration point number. All line elements use full integration for the application of external loads. For distributed loads applied to the ends of the element, NPT corresponds to the end number of the element.
KSTEP: Step number.
KINC: Increment number.