## 5 Analysis of Experimental and Simulation Results
### Thermally-Stratified Water Body Conditions
#### 5.2.2 Case 6 Working Conditions  
In Case 6, the initial velocity of the jet is 0.2 m/s, with a depth of 0.26 m and a temperature difference of 10 \({}^{\circ}\)C compared to the ambient water. The background stratification temperature difference of the ambient water is 4 \({}^{\circ}\)C. The initial velocity and depth remain unchanged from Case 5, but the initial velocity of the jet has doubled. Under these experimental conditions, changes in the temperature field distribution of the jet discharged into a uniform water body environment at time intervals of 5 s, 10 s, 15 s, 20 s, 25 s, and 30 s are shown in Figure 16.  
When the jet velocity increased from 0.1 m/s to 0.2 m/s, during the initial 10 s of the jet discharge, the temperature diffusion of the jet is predominantly non-vertical, with a vertical temperature diffusion height of less than 3 cm and a horizontal temperature diffusion distance gradually increasing from 10 cm to 20 cm. The temperature difference between the main body temperature diffusion area of the jet and the surrounding water body is approximately 3 \({}^{\circ}\)C. By the 15 th second of the jet discharge, there is a gradual vertical diffusion trend in the jet temperature, with a vertical temperature diffusion spacing of 4 cm and an upward height of 5 cm. The ambient water body's temperature difference within the temperature diffusion area accounts for approximately half (50%). At 20 s, there is an upward diffusion of the jet temperature towards a layered interface, with a horizontal diffusion distance reaching 35 cm. In comparison to Case 5 conditions, this represents a 25% increase in the horizontal diffusion rate. However, due to density effects at these layers, upward vertical diffusion ceases. As time progresses and as it moves rightwards for another five seconds after arriving at a stratified interface, the overall decrease in temperature difference between its surroundings becomes less than 1 \({}^{\circ}\)C, while showing an increased horizontal spread reaching up to 42 cm. Compared to Case 5 conditions, both the horizontal diffusion distance of the jet temperature and the diffusion rate are increased by 20%. By 30 s, the temperature difference between the jet temperature diffusion area and the ambient water body stabilizes within 1 \({}^{\circ}\)C. The horizontal diffusion distance of the jet temperature reaches 49 cm. This is different from Case 5 conditions as a small part of the temperature diffusion area floats up to a height of 10-13 cm. However, the entire jet temperature diffusion area still remains situated beneath the stratified interface. Both  
Figure 16: Temporal variation of the thermal jet temperature field under the experimental conditions.  
the horizontal diffusion distance and the diffusion rate of the jet temperature have been enhanced by 32%.  
Based on the experimental condition's measurement time, moments of 5 s, 10 s, 15 s, 20 s, 25 s, and 30 s are selected from the Case 6 simulation calculations for analysis. These results are shown in Figure 17.  
When the jet velocity doubles, the diffusion of the jet temperature is primarily driven by horizontal movement. Up until 15 s, there is an apparent upward floating trend in the diffusion of the jet temperature. The vertical range of temperature diffusion is limited, while the horizontal distance increases rapidly. In comparison to Case 5 conditions, there is a 20% increase in the overall jet temperature diffusion rate in the horizontal direction. As the jet temperature slowly diffuses upwards, it eventually reaches a layered interface where it is influenced by the density gradient. This causes a significant decrease in the vertical floating rate of the jet. However, due to its initial momentum, part of the jet's temperature diffusion area remains above this layered interface. Subsequently, dominant horizontal diffusion movement begins, as opposed to the overall vertical temperature diffusion distance being relatively small for the jet at this point.