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Objects and Methods : Power Reservoir Methods : User Methods : Cavitation
Cavitation
This category depends on selecting the Unit Power Table method and contains methods for dealing with the problem of cavitation on turbines. Cavitation is the sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces and this process can cause damage to turbines under certain operating conditions.
* None
This is the default, do-nothing method.
* Unit Head and Tailwater Based Regions
This method allows the user to specify the regions of operation in which cavitation does NOT occurs, so that these regions can be avoided. These regions can be dependent on both operating head and tailwater.
Slots Specific to This Method
Note:  Many of these slots have column or row dimensions based on the number of units. The rows/columns of these slots are expanded at the beginning of the run to match the value in the Number of Units slot. When first configuring this method, the user must enter the Number of Units, then run the model (stepping through one timestep is enough) to grow the slots to the right dimensions.
 Unit Power Cavitation Table
Type: TableSlot
Units: Length, Length, Power, and Power
Description: This table represents the region of operation that does not cause cavitations.
Information: The table will have one block per unit and four columns per block: head, tailwater, and minimum power to prevent cavitation, and maximum power to prevent cavitation. Interpolation of this table will be used to determine the feasibility for each flow-head combinations in the Unit Power Table. Some combinations may not be feasible at any tailwater, and these combinations should not be used in optimization or simulation. Others will have a minimum tailwater level for feasibility. For some units, tailwater may not affect cavitation. In these cases two rows should be used for each head: one with minimum tailwater and one with maximum tailwater.
I/O: Required Input
 
Unit 1
Unit 2
Tailwater (ft)
Operating Head (ft)
Min. Non-Cav. Power
(MW)
Max. non-Cav. Power
(MW)
Tailwater (ft)
Operating Head (ft)
Min. Non-Cav. Power
(MW)
Max. non-Cav. Power
(MW)
2067
100
1
12
2067
100
2
10
2067
200
1.1
12.5
2067
200
3
11
2067
300
1.4
12.6
2067
300
3.5
12
2116
100
2
12
2116
100
2
10
2116
200
2.1
12.3
2116
200
3
11
2116
300
2.5
12.8
2116
300
3.5
12
 Unit Cavitation Optimization Tolerances
Type: Table
Units: Fraction, Fraction
Description: Tolerance used to adjust the cavitation region in Optimization.
Information: This slot is used to shrink the cavitation region in Optimization, to avoid the possibility of optimal solutions that when run in the Rulebased Simulation just barely dip into a cavitation zone. For example, if 0.01 is specified, this translates to giving the optimization a one percent cushion to avoid the cavitation zone. There is one row for each unit.
I/O: Optional Input
Method Details 
In Simulation, the dispatch method will execute this method once head, tailwater elevation, and power are computed for each unit. This method will determine if the computed head, tailwater elevation, and power fall outside of the minimum and maximum power to prevent cavitation regions. If so, the method will issue an error but not stop the run. If the method is called and there is no valid Unit Power, then the method is exited without performing any computations.
Revised: 07/17/2020