In the transient analysis program, one may be able to get different forces (as a function of time) for different piping components. #PIPENET SOFTWARE#The values in the case of a fluid hammer are usually got from a transient flow analysis software which outputs the results of a fluid hammer in terms of forces on a system as a function of time. CAEPIPE takes these values at each timestep (linearly interpolates if necessary) and multiplies it by the user-input scale factor and applies it in the user specified direction (FX, MY etc.). These values may be forces/moments in the case of a fluid hammer problem. The time functions that CAEPIPE requires can be any time-varying quantity. Are time functions momentum forces or pressures or equivalent forces of deflections?Ī-3. But if you choose Time history under Results menu (Output), then the whole RTH file is displayed (of course, as Displ, Support loads).Īt a particular node, one can input the FX, FY, FZ as separate Time Varying loads and CAEPIPE will calculate the resultant. under Support loads, Pipe element forces, Displacements for Time history load case. CAEPIPE scans this file (.RTH) and finds the maximums and reports these results for forces/moments/displacements etc. only) at every 0.1 sec from 0.1 to 20 seconds. Enter 5 not 0.05 for 5%.ĬAEPIPE calculates the solutions (modal displ. Damping: Is the damping factor expressed as a percentage (not as a fraction). The file name that contains all these results is model.RTH.Ĥ. You need to check the "Save Results" checkbox (or press F2 in the v4.1 and earlier). For example: if you wanted to see results for every 5th time step (0.5s, 1s, 1.5s, 2s and so on), enter 5. Output interval: Is the periodic time step you want CAEPIPE to report results. ForĮxample, the effect of a really heavy steam hammer could linger on for a minute, and your forcing function data could span only 8 sec.ģ. But, CAEPIPE can compute system response to that forcing function well after the forcing function ceases. The time function is only the forcing function. The (time step times number of time steps) may exceed the range of available data in the timeįunction. Number of time steps: is how long you want to study system response. (typically no more than 10% of the period of the highest natural frequency, i.e., higher the frequency, smaller the time step, e.g. Time step: is the smallest time gap for which you want to compute system response. Explanation of terms in the Time History Analysis control dialog (found in the Layout window > Loads menu > Time History)ġ. It is possible to fill in up to 1000 rows of time-value pairs. You can delete a time function (use Ctrl+X). Time functions can be renamed inside CAEPIPE. The above format can be followed to create indvidual text files that contain one time function, and can be read into CAEPIPE. The time function above is illustrative and not a guideline. Time history analysis begins at time t=0.0.Īn Illustrative time function (format: time value) Example: 0.0 0.0 (you must have a zero entry for the Value, otherwise CAEPIPE will interpolate linearly for a smaller time, say t=0.1, if this time is smaller than that available in the table (say you had started from 0.2 12000). You can make that table as fine as you want it to be. In CAEPIPE, the time function you define can have any interval between two time values. The actual force (or moment) at any time is found by linear interpolation between time points and multiplying by the input scale factor. which describe the variation of the forcing function with respect to time. #PIPENET SERIES#Time functions are non-dimensional (i.e., a series of time versus value tables). These separate force-time histories are then applied separately as Time Varying Loads in CAEPIPE at the corresponding nodes in the piping model. Typically, a transient fluid flow analysis program computes forces as a function of time at all changes in directions (bends/tees) resulting from a transient event (such as a fluid hammer). What are time functions and how do I use them?Ī-1.
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