Chapter 1509: Power of Domestic Aircraft Carriers

Five hours later, at Lushun base, data computing center.

When the first set of airflow field visualization images appeared on the screen, Chang Haonan immediately stood up and strode to the front of the screen. He sometimes moved his eyes quickly on the colorful streamline diagram, and sometimes drew circles in specific areas with his fingers.

The others did not dare to disturb him until Chang Haonan returned to his seat. Only then did Shi Wenqiang walk tremblingly behind the podium.

When he was in the Torch Laboratory, he also participated in a group meeting with Chang Haonan in attendance, but at that time it was just a simple teacher-student relationship, and even if something went wrong, it would be resolved with just a few words of criticism.

However, in this situation...

Shi Wenqiang certainly knew that this was the segment Guo Chunyu specially prepared for him to perform.

but……

I swear to God, he was just a newbie who had been working for less than two years. Just three days ago, he rarely saw his direct superior, Director Guo Chunyu.

But now, he had to give a report to Chang Haonan.

Weak, pitiful, and helpless.jpg

Finally, after preparing himself mentally, Comrade Xiao Shi mustered up the courage to speak:

"The airflow field of large ships is relatively complex when they are actually sailing, so we selected several typical working conditions for measurement and prepared to compare the measurement results with the 'rooster wake' flow field model obtained by CFD calculation and wind tunnel simulation..."

"..."

Obviously, the young man was well prepared.

But, it's a little too sufficient.

In this race against time, we can only focus on the key points.

Therefore, after listening to the first introduction, Chang Haonan directly circled two sets of data on the screen with a laser pen:

“Here, and here, the vorticity distribution is asymmetric.”

The air suddenly became quiet.

"Pay attention to your working conditions 1, 3, and 4." Chang Haonan simply continued speaking to the notebook in front of him, "When the ship is sailing straight at a speed of 32 knots and without rolling, the curve changes relatively smoothly. The vorticity starts to rise rapidly from the front end of the bow deck, reaches its peak slightly behind the midship, and then falls back rapidly."

It was not until this time that Shi Wenqiang finally reacted and quickly adjusted the corresponding result on the screen to the corresponding working condition 1.

But Chang Haonan has already entered the next part:

"When the ship is sailing straight at a speed of 32 knots, but with a 3° left tilt, the vorticity of the airflow field starts to rise rapidly from the front end of the deck, reaches a maximum value after about 100m, and then falls back. The vorticity of the airflow field rises rapidly in the rear 1/3 deck section, reaches a maximum value near the stern, and then falls back rapidly. The change of the wake vorticity is relatively gentle; when there is a 3° right tilt, the vorticity change trend is similar to that of the left tilt, but the vorticity value is much smaller than the left tilt..."

Shi Wenqiang tried hard to keep up with the opponent's pace, and then found that it was true.

And these are not even the parts he has yet to report——

In fact, not only has it not been reported yet.

These results were calculated just in the past five hours, and even Guo Chunyu might not be able to understand such details.

“How do you compare it with the computational model?”

Chang Haonan's questions were brief and powerful.

"When the ship was sailing straight without rolling and tilted 3° to the left, the simulation and the actual measurement were basically consistent, with an error of less than 4%. But when the ship tilted 3° to the right..." Faced with this situation, Shi Wenqiang calmed down and operated the computer to call up another set of images. "The measured vorticity value was 17% lower than the model prediction. We repeatedly checked the measurement equipment and methods and ruled out the possibility of technical errors."

Faced with this result, everyone looked at each other in bewilderment.

A few minutes later, Bi Fengchun, who had been silent until then, from the Operations Center of the Carrier Aircraft Training Base, spoke up: "For experienced pilots, a 17% flow field deviation will not cause a landing failure, but it will undoubtedly increase the operating pressure during landing."

This result is actually not surprising to everyone.

Otherwise, all the aircraft carriers that have not undergone ship surface flow field measurements will be useless.

Of course, the less deviation there is, the better.

In order to adapt to the take-off and landing of jet aircraft on aircraft carriers, the Americans crashed hundreds or even thousands of carrier-based aircraft.

But it does not mean that China has to repeat this process completely.

After a brief pause, Bi Fengchun continued:

"In addition, if we want to deploy drones on aircraft carriers in the future, such an error may be unacceptable..."

Chang Haonan raised his hand and pressed it down, signaling everyone to stay calm:

“We will continue to process the next phase of data, and similar situations should appear in the data corresponding to different wind directions.”

……

Another few hours passed.

That night, the computing center of the Lushun base was brightly lit.

Twenty high-performance servers were running at full speed, and the hum of the cooling system filled the entire room.

Chang Haonan stood in front of the main console, his eyes fixed on the constantly updated data stream on the screen.

"Academician Chang, the third set of comparison data is out." Guo Chunyu's voice came from behind, "Just as you predicted, the flow field distribution on the deck surface is basically consistent with the calculation model in the two cases of 0° wind and 15° wind on the port side, but there is a 15% deviation when the wind is 17.3° on the starboard side."

Chang Haonan nodded and continued to look at the screen in front of him in silence.

For a moment, the huge computer center fell silent.

No one asked why.

For a large ship with asymmetric left-right relations, there could only be one reason for this to happen.

Island interference.

Even a layman can guess it.

The key is how to solve this problem.

Chang Haonan's fingers flew across the keyboard, calling up a set of complex equations: "The low Mach number turbulent flow field generated by the island has obvious scale effects. The traditional RANS model cannot accurately capture this large-scale low-speed separation flow, and the wind tunnel cannot use a 1:1 300-meter-long aircraft carrier model to blow, so the model calculation results will have a certain... irregular deviation from the actual data."

Guo Chunyu pushed his glasses and realized where his omission lay.

The Institute of Aerodynamics itself is an aviation research unit, and the aircraft is faster and relatively smaller in size, so this deviation can basically be ignored.

But it doesn't work well on a boat.

At this time, Chang Haonan concluded:

"In the final analysis, the reason for this situation is that the Liaosheng ship's island is too large and located relatively forward, which happens to cause the strongest wake field on the island to correspond to the aircraft's landing area."

The faces of the people around him became solemn.

Obviously, this is a problem that cannot be solved, at least not in Liao Province.

The hull of 1143.6 is ready-made. Not to mention that it is about to be put into service, even if these details were known at the beginning of the transformation, it would be impossible to dismantle the island.

In fact, the reason why the measurement of airflow field on a real ship is considered a non-essential supplementary subject in any country is that this process is completely afterthought.

You need to build the aircraft carrier first before you can measure the airflow field of the actual ship.

But at this time, even if the measurement reveals defects, it is impossible to dismantle the aircraft carrier and rebuild it.

We can only wait for the next ship to make changes.

Most countries only have 1-2 aircraft carriers, so it is not worth the hassle.

"It's better to have a reminder than nothing." Bi Fengchun comforted, "I will remind the pilots to pay special attention to the right bank angle and right wind..."

At this time, Chang Haonan suddenly hit the Enter key on the keyboard hard.

The crisp sound was particularly abrupt in the silent computing center and instantly attracted everyone's attention.

"I can come up with a large eddy simulation turbulence model that is specifically corrected for low Mach numbers and large-scale flow fields."

Chang Haonan turned the screen around and displayed the densely packed calculation results in front of everyone:

"Although the original design of the Liaosheng cannot be modified, the model can be linked to the landing aid system. Although it still cannot cope with the countless situations that may occur in reality, it can at least allow pilots to be prepared for possible turbulence."

Guo Chunyu wiped the sweat off his head and said, "But Academician Chang, if we use LES large eddy simulation instead, the amount of calculation will increase exponentially..."

"So we only use LES for the area near the island, and RANS for the rest." Chang Haonan quickly drew a schematic diagram, "Here, here, and here, set up transition zones. Director Guo, I need you to re-divide the calculation grid, especially the area within 50 meters behind the island..."

"..."

Guo Chunyu immediately organized the team to start working. The atmosphere in the computing center became tense and orderly. Engineers were divided into three shifts to ensure that the calculations were carried out uninterruptedly.

Chang Haonan never left the console. His mind seemed to be integrated with the computer, constantly adjusting parameters and optimizing algorithms.

At three o'clock in the morning, Du Lin quietly walked into the computing center.

He wanted to ask about the progress, but after seeing Chang Haonan leaning back in his chair to rest, he chose to bypass the main console and go to Guo Chunyu who was processing parameters.

"How...can you do it?" Du Lin asked uncertainly.

"It is theoretically feasible." Guo Chunyu replied in a low voice, holding a freshly printed calculation result in his hand. "Academician Chang's hybrid LES-RANS model has reduced the average error to 12%..."

"No, that's not enough." At this time, Chang Haonan suddenly popped up from behind, "We need to consider another factor - the coupling effect of the ship's motion and airflow."

He walked quickly to the whiteboard and grabbed a marker. "The wake field of the island is not only affected by the wind speed, but also related to the roll and pitch motion of the ship. This is a six-degree-of-freedom coupling problem..."

As Chang Haonan drew a series of complex equations on the whiteboard, the engineers in the room gradually gathered around. Some began to discuss in a low voice, while others quickly recorded the key points.

"So we need to add a ship motion module to the model?" asked Shi Wenqiang.

Chang Haonan nodded: "And it needs to be updated in real time, combined with the attitude sensor on the aircraft carrier... I used aviation terms, but there should be something similar."

“Of course, the attitude reference system has an accuracy of 0.1 degrees.”

"Perfect." Chang Haonan turned to Guo Chunyu, "Reset the boundary conditions, use the ship's motion parameters as time-varying input, and prepare for a new round of calculations."

……

As the early morning sun shone through the windows of the computing center, a new round of results was finally generated on the screen.

"How much has the error been reduced to?" Du Lin's voice came.

It was obvious that he had not slept all night. His military uniform was still straight, but the fatigue on his face could not be concealed.

"8.3%." Chang Haonan rubbed his temple. "This is the best result that can be achieved so far. It will definitely be no problem for manned aircraft, but for drones..."

He thought for a moment and said, "It's hanging."

"If we want to further reduce the error, we can only start with hardware - reducing the size of the island and changing its position at the same time."

This sentence obviously has a hidden meaning.

Du Lin also reacted immediately.

He sat down next to Chang Haonan and said, "It has been decided that the domestically produced aircraft carrier will use an integrated power system, and there is no longer a rigid requirement for the location of the engine room."

Chang Haonan closed his eyes and rested, but he continued, "But if you want to achieve a ship island effect similar to that of a nuclear-powered aircraft carrier, you need to use a heavy-duty gas turbine that is smaller in size and produces less exhaust emissions."

"I can't make the final decision on this." Du Lin shook his head, "But I will report the situation to my superiors as an important reference in the decision-making process."