1. A non-transitory computer-readable recording medium in which a thermal hydraulic simulating program that instructs a computer to carry out a simulation of a velocity field and/or a temperature field, the program instructing the computer to execute: carrying out the simulation by solving a thermal hydraulic equation on the basis of an analysis condition in each time step; modifying the analysis condition; when the analysis condition is modified while the simulation is being carried out, storing data related to the modified analysis condition in a memory region; after completion of the simulation in a first time step being carried out at the modifying the analysis condition and before start of the simulation in a second time step after the first time step, referring to the data related to the modified analysis condition stored in the memory region; carrying out the simulation based on the data related to the modified analysis condition in the second time step; displaying a three-dimensional (3D) model representing a space including the velocity field and/or the temperature field on a monitor; and if a sliding mechanism having an opening ratio varying with sliding of the sliding mechanism is slid on the 3D model displayed on the monitor, modifying a resistance, serving as a resistance condition of the sliding mechanism and included in the analysis condition, in accordance to the opening ratio varied through the sliding.