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CALCULATOR MODULE : Dimensionless Number ±
Calculate dimensionless numbers for fluid flow and other physical systems. Dimensionless numbers are calculated from groups of variables so that the result is dimensionless. Dimensionless numbers can be calculated from any consistent set of units, and will have the same value. Dimensionless numbers can be a very powerful tool for analysing physical systems. Change Module : Related Modules : |
CALCULATOR MODULE : Water Hammer Transient Pressure ±
Calculate water hammer transient pressure and pressure wave velocity. Water hammer is caused by a sudden reduction of flow rate in liquid pipelines. Water hammer commonly occurs in water pipes, but it can occur in any liquid piping system. The transient pressure is reduced if gas is present in the liquid, or if the effective shut off time is greater than the maximum shut off time. The maximum shut off time is the time taken for the pressure transient to travel to the pipe inlet, and back again. Change Module : Related Modules : |
CALCULATOR MODULE : Transient Pressure Wave Velocity ±
Calculate water hammer transient pressure wave velocity. A sudden reduction of velocity in a liquid pipeline initiates a pressure wave which travels to the pipe inlet, and then back. The wave velocity increases with pipe stiffness. Any gas present in the liquid reduces the pressure wave velocity. The maximum shut off time is the time taken for the pressure transient to travel to the pipe inlet, and back again. Change Module : Related Modules : |
CALCULATOR MODULE : Airy Linear Gravity Wave ±
Calculate Airy wave velocity, acceleration and surface profile. The Airy linear gravity wave theory is a first order model of freshwater and seawater gravity waves. The Airy wave is assumed to have a simple sinusoidal (first order harmonic) profile which is a reasonable approximation for small amplitude deep water waves. As the wave amplitude increases and or the water depth decreases the waves tend to become more peaky and are no longer a simple sinusoidal shape. The Airy wave model is then less accurate for analysing water particle motions. For large amplitude waves, or shallow water waves other wave models such as Stokes wave or Cnoidal wave should be used. The recommended wave type is displayed below the calc bar. Check that the convergence is close to or equal to one. The wave period should be measured at zero current velocity to avoid Doppler effects. Related Modules : |
CALCULATOR MODULE : Stokes Fifth Order Wave ±
Calculate Stokes wave velocity, acceleration and surface profile using Skjelbria and Hendrickson's fifth order wave method. Stokes wave model is suitable for waves with short wavelength or small amplitude. The calculators include the correction to the sign of the c 8 term in the C2 coefficient (changed from + to -2592 c 8 ). Check that the convergence is close to or equal to one. The wave period should be measured at zero current velocity to avoid Doppler effects. Note : The Stokes wave theory uses a truncated infinite series. The truncated series is only valid for certain conditions. For shallow water waves the cnoidal wave is recommended. The recommended wave type is displayed below the calc bar. Reference : Lars Skjelbria and James Hendrickson, Fifth Order Gravity Wave Theory Related Modules : |
CALCULATOR MODULE : Cnoidal Fifth Order Wave ±
Calculate Cnoidal wave velocity, acceleration and surface profile using Fentons 1999 fifth order wave method. The Cnoidal wave is defined by the elliptic modulus m, the wave trough depth w, and the wave alpha parameter α. The Cnoidal wave model is a truncated series and is only valid within certain ranges. The Cnoidal wave theory is not recommended where the wavelength over water depth ratio (Lod) is less than 8. The recommended wave type is displayed below the calc bar. Note : The cnoidal wave theory uses a truncated infinite series. The truncated series is only valid for conditions where the series converges (m > 0.8). For deep water waves with small m, the series does not converge (use the Stokes wave instead). Check that the convergence is close to or equal to one. The wave period should be measured at zero current velocity to avoid Doppler effects. Reference : J D Fenton, The Cnoidal Theory Of Water Waves, Developments in Offshore Engineering, Gulf, Houston, chapter 2, 1999 Related Modules : |
CALCULATOR MODULE : Morison's Equation Wave And Current Load ±
Calculate wave and current loads on submerged structures using Morison's equation (Airy Stokes and Cnoidal waves). For vertical structures the load forces are due to the horizontal velocity and acceleration only. For horizontal structures the load forces also include vertical velocity and acceleration. Lateral (lift) forces are due to non symmetric flow around the structure, either because of proximity to the seabed or another structure, or by non symmetric cross section. The Keulegan Carpenter number is a measure of the ratio of wave inertial forces and drag forces. Change Module : |
CALCULATOR MODULE : Ocean Wave And Current Velocity And Acceleration ±
Calculate ocean wave and current velocity and acceleration for Airy, Stokes, cnoidal and JONSWAP waves. Wave velocity and acceleration can be calculated for Airy, Stokes, and Cnoidal waves. The recommended wave type is displayed below the calc bar. Use the Result Plot option to compare the Airy, Stokes, and cnoidal wave profiles. The seabed significant wave velocity and zero upcrossing period can be calculated from the JONSWAP surface spectrum. Current velocity can be calculated near the seabed using either the logarithmic profile, or the 1/7th power law profile. The logarithmic and power law profiles are not valid For large elevations above the seabed. Note : The Stokes and cnoidal waves use trucated infinite series. Under certain conditions the truncated series do not converge properly. The Stokes wave is not suitable for shallow water waves. The cnoidal wave is not suitable for deep water waves. The recommended wave type is displayed below the calc bar. The JONSWAP wave uses an Airy wave transfer function to calculate seabed velocity. The JONSWAP wave is not suitable for very shallow waves (near breaking). Change Module : |
CALCULATOR MODULE : Ocean Wave Velocity And Acceleration ±
Calculate ocean wave velocity and acceleration for Airy, Stokes, cnoidal and JONSWAP waves. Wave velocity and acceleration can be calculated for Airy, Stokes, and Cnoidal waves. The recommended wave type is displayed below the calc bar. Use the Result Plot option to compare the Airy, Stokes, and cnoidal wave profiles. The seabed significant wave velocity and zero upcrossing period can be calculated from the JONSWAP surface spectrum. Note : The Stokes and cnoidal waves use trucated infinite series. Under certain conditions the truncated series do not converge properly. The Stokes wave is not suitable for shallow water waves. The cnoidal wave is not suitable for deep water waves. The recommended wave type is displayed below the calc bar. The JONSWAP wave uses an Airy wave transfer function to calculate seabed velocity. The JONSWAP wave is not suitable for very shallow waves (near breaking). Change Module : |
CALCULATOR MODULE : Ocean Wave Directionality And Spreading ±
Calculate ocean wave velocity reduction factor from relative heading and spreading factor. The spreading factor accounts for wave "choppiness" or superimposed multi directional waves. Locally generated waves are generally short crested and more "choppy", and are characterised by small spreading factors. Long range swells are generally long crested uni directional waves, and are characterised by large spreading factors. Change Module : |
CALCULATOR MODULE : Ocean Wave Probability And Return Period ±
Calculate ocean wave height and period from return period data using the Weibull, Gumbel or Frechet probability distributions. The three parameter distribution and Z offset is used to account for a minimum value, the smallest event which can occur in any sample period. The best fit line is calculated for the data points using the least squares linear regression method. The regression is calculated for return period versus amplitude (the X and Z values are swapped). The regression data points and regression parameters are displayed in the output view at the bottom of the page. Change Module : Related Modules : |
CALCULATOR MODULE : Ocean Wave And Current Probability And Return Period ±
Calculate ocean wave height, wave period and current velocity from return period data using the Weibull, Gumbel or Frechet probability distributions. The three parameter distribution and Z offset is used to account for a minimum value, the smallest event which can occur in any sample period. The best fit line is calculated for the data points using the least squares linear regression method. The regression is calculated for return period versus amplitude (the X and Z values are swapped). Use the Data Plot option on the plot bar to display the data points and the calculated best fit. The regression data points and regression parameters are displayed in the output view at the bottom of the page. Change Module : Related Modules : |
CALCULATOR MODULE : JONSWAP Wave Velocity And Period ±
Calculate JONSWAP wave seabed velocity and zero upcrossing period from spectral moments. The seabed velocity and upcrossing period is calculated using a first order Airy wave transformation. The Airy wave transformation may not be valid in shallow water. The calculation has been optimised for elevations on or near the seabed, and is not recommended for elevations greater than half the water depth. Return period data can be analysed using either the Weibull, Gumbel or Frechet distribution. Reference : Hasselmann K et al : Measurements of Wind-Wave Growth And Swell Decay During The Joint North Sea Wave Project (JONSWAP) Change Module : |
CALCULATOR MODULE : JONSWAP Wave Directionality And Spreading ±
Calculate JONSWAP wave spreading and velocity reduction factor from relative heading and spreading factor. Wave spreading accounts for the effect of short crested "choppy" waves with non uniform velocity and heading. By comparison, long ocean swells tend to have uniform velocity and direction, expecially in mid ocean. Use small spreading factors for "choppy" waves, and large spreading factors for ocena swells. Reference : Hasselmann K et al : Measurements of Wind-Wave Growth And Swell Decay During The Joint North Sea Wave Project (JONSWAP) Change Module : |
CALCULATOR MODULE : JONSWAP Combined Wave And Current Velocity ±
Calculate JONSWAP seabed wave and current amplitude from return period data. Return period data can be analysed using either the Weibull, Gumbel or Frechet distribution. Current velocity can be calculated using either the logarithmic profile, or the 1/7th power law profile. The logarithmic and power law profiles are only valid in the boundary layer on or near the seabed. The seabed velocity and upcrossing period is calculated from the JONSWAP surface spectrum using a first order Airy wave transformation. The calculation may not be valid in shallow water, and is not recommended for elevations greater than half the water depth. Reference : Hasselmann K et al : Measurements of Wind-Wave Growth And Swell Decay During The Joint North Sea Wave Project (JONSWAP) Change Module : |
CALCULATOR MODULE : DNVGL RP F109 Wave Seabed Velocity ±
Calculate DNVGL RP-F109 wave seabed velocity from the JONSWAP surface spectrum. An Airy wave transform is used to calculate the significant seabed velocity, and zero upcrossing wave period. The calculation is not valid in shallow water, or at elevations greater than half the water depth. Reference : DNVGL-RP-F109 : On-Bottom Stability Design Of Submarine Pipelines (Download from the DNVGL website) Change Module : |