MGS 3100
Continuous Simulation Example of Truck Unloading Problem
Explanations of Column Items going from left to write on the Excel solution
Truck# column shows the truck numbers
Arrival Interval shows randomly generated intervals [-ln(rand())*$C$2 where $C$2 is the average arrival interval, 0.6 in this problem], exponentially distributed with average of 0.6
Truck Arrives At shows actual arrival time on a continuous time clock which is previous truck's arrival time plus the arrival interval of the current (or arriving) truck. The clock is initiated at zero in the beginning of the simulation and thus the first truck always arrives at 0 plus its arrival interval.
Wait Time computes wait time in queue - compare arrival of a truck with the departure (service ending) time of the previous truck. For instance, truck 10 arrives at 5.11, but truck 9 finishes only at 6.41. Thus, truck 10 must wait until then [6.41-5.11=1.30 hours].
Service Begins At shows Service begin time, which is arrival time plus the wait time for a truck.
Loading Time shows randomly generated loading times - computed just like Arrival Intervals in column B, but with a mean of 0.5 hours (use $G$2 instead of $C$2).
Service Ends At shows the service ending time computed as Service begin time + loading time.
Last Truck That Left System uses the VLOOKUP statement to check arrival time of a truck against departures of previous ones to see which truck left last. For instance, when truck 10 arrives at 5.11, truck 5 was the last one to have already left at 5.06. Thus, 6, 7, 8, and 9 are the 4 trucks in the system ahead of it.
Trucks in System computes the above by simply subtracting 5 from 10, and then subtracting one more because truck 10 is not yet counted as being in the system.
Trucks in Queue shows number in queue, which is always one less than number in system, unless that number is 0.