Johns Hopkins Turbulence Databases

Database Functions

For detailed formulae used in the functions, DOWNLOAD DOCUMENT
  Isotropic MHD Channel Mixing
GetVelocity
GetMagneticField      
GetVectorPotential      
GetPressure
GetVelocityAndPressure
GetForce    
GetVelocityGradient*
GetMagneticFieldGradient*      
GetVectorPotentialGradient*      
GetPressureGradient
GetPressureHessian
GetVelocityLaplacian
GetMagneticFieldLaplacian      
GetVectorPotentialLaplacian      
GetVelocityHessian
GetMagneticFieldHessian      
GetVectorPotentialHessian      
GetPosition
GetBoxFilter  
GetBoxFilterSGSscalar  
GetBoxFilterSGSvector  
GetBoxFilterSGSsymtensor  
GetBoxFilterSGStensor  
GetBoxFilterGradient  
GetDensity      
GetDensityGradient      
GetDensityHessian      
GetThreshold



*Note: The divergence-free condition in the simulation is enforced based on the spectral representation of the derivatives. The JHTDB analysis tools for gradients are based on finite differencing of various orders. Therefore, when evaluating the divergence using these spatially more localized derivative operators, a non-negligible error in the divergence is obtained, as expected.

Database Spatial Differentiation Options:

Options for GetVelocityGradient, GetMagneticFieldGradient, GetVectorPotentialGradient, GetPressureGradient and GetDensityGradient

FD4: 4th-order centered finite differencing (can be spatially interpolated)
FD6: 6th-order centered finite differencing (without spatial interpolation)
FD8: 8th-order centered finite differencing (without spatial interpolation)
M1Q4: Splines with smoothness 1 (3rd order) over 4 data points.
M2Q8: Splines with smoothness 2 (5th order) over 8 data points.
M2Q14: Splines with smoothness 2 (5th order) over 14 data points.

Options for GetPressureHessian, GetVelocityLaplacian, GetMagneticFieldLaplacian, GetVectorPotentialLaplacian, GetVelocityHessian, GetMagneticFieldHessian and GetVectorPotentialHessian

FD4: 4th-order centered finite differencing (can be spatially interpolated)
FD6: 6th-order centered finite differencing (without spatial interpolation)
FD8: 8th-order centered finite differencing (without spatial interpolation)
M2Q8: Splines with smoothness 2 (5th order) over 8 data points.
M2Q14: Splines with smoothness 2 (5th order) over 14 data points.

Database Spatial Interpolation Options:

Interpolation options for GetVelocity, GetMagneticField, GetVectorPotential, GetPressure, GetVelocityAndPressure, GetDensity and GetPosition

NoSInt: No Space interpolation (value at the datapoint closest to each coordinate value)
Lag4: 4th-order Lagrange Polynomial interpolation along each spatial direction|
Lag6: 6th-order Lagrange Polynomial interpolation along each spatial direction
Lag8: 8th-order Lagrange Polynomial interpolation along each spatial direction
M1Q4: Splines with smoothness 1 (3rd order) over 4 data points.
M2Q8: Splines with smoothness 2 (5th order) over 8 data points.
M2Q14: Splines with smoothness 2 (5th order) over 14 data points.

Interpolation options for GetVelocityGradient, GetMagneticFieldGradient, GetVectorPotentialGradient, GetPressureGradient, GetDensityGradeint, GetPressureHessian, GetVelocityLaplacian, GetMagneticFieldLaplacian, GetVectorPotentialLaplacian, GetVelocityHessian, GetMagneticFieldHessian, GetVectorPotentialHessian and GetDensityHessian

FD4NoInt: No interpolation (value of the 4th order finite-difference evaluations at the datapoint closest to each coordinate value is returned)
FD6NoInt: No interpolation (value of the 6th order finite-difference evaluations at the datapoint closest to each coordinate value is returned)
FD8NoInt: No interpolation (value of the 8th order finite-difference evaluations at the datapoint closest to each coordinate value is returned)

FD4Lag4: 4th-order Lagrange Polynomial interpolation in each direction, of the 4th-order finite difference values on the grid.
M2Q8: Splines with smoothness 2 (5th order) over 8 data points.
M2Q14: Splines with smoothness 2 (5th order) over 14 data points.

Database Time Interpolation Options:

For all variables and derivatives listed above, the two options are:

NoTInt: No interpolation (the value at the closest stored time will be returned).

PCHIP: Piecewise Cubic Hermite Interpolation Polynomial method is used, in which the value from the two nearest time points is interpolated at time t using Cubic Hermite Interpolation Polynomial, with centered finite difference evaluation of the end-point time derivatives (i.e. a total of four temporal points are used).

Database Spatial Filtering Options:

Options for GetBoxFilter, GetBoxFilterSGSscalar, GetBoxFilterSGSvector, GetBoxFilterSGSsymtensor, GetBoxFilterSGStensor and GetBoxFilterGradient:

Field: The field or combination of fields, which should be filtered.
For the GetBoxFilter, GetBoxFilterGradient and GetBoxFilterSGSsymtensor the valid options are -- "velocity" or "u", "magnetic" or "b", "potential" or "a", "pressure" or "p", density or "d".
For the GetBoxFilterSGSscalar, GetBoxFilterSGSvector, GetBoxFilterSGStensor two fields should be specified using single characters, such as "pd", "up" or "ub".
GetBoxFilterSGSscalar operates on two scalar fields, e.g. "pp" or "pd".
GetBoxFilterSGSvector operates on a vector and a scalar field, e.g. "up" or "bp".
GetBoxFilterSGStensor operates on two vector fields, e.g. "ub" or "ba".

Filter width (odd multiple of the grid resolution): Size of the box filter to be applied along each spatial direction. NOTE: This value will be rounded to the nearest odd multiple of the grid resolution.

Additional option for GetBoxFilterGradient:

Spacing (multiple of the grid resolution): The finite differencing spacing that should be used.

Database Threshold Options:

Options for GetThreshold:

Field (one of vorticity, Q, velocity, magnetic, potential, pressure, density): The field, which should be thresholded.

X, Y, Z, Xwidth, Ywidth, Zwidth: The spatial region to be examined. X, Y and Z specify the grid node to be used as the bottom left corner of a box, and Xwidth, Ywidth and Zwidth specify the box's dimensions. NOTE: These options are similar to those used for the GetRawData functions and the cutout service.

Returns: All grid locations from the specified region, at which the norm of the given field is above the given threshold, and the norm of the field at each of these locations.

 

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Last update: 10/7/2016 10:40:18 AM