However, just a few seconds later, Chen Zhuo’s brow furrowed.
What appeared on the screen was not at all the smooth, elegant aerodynamic curve he had been expecting.
It was a chaotic mess.
The red and green lines representing the data from each pressure sensor, like a swarm of startled snakes, shot wildly up and down the coordinate axes.
The edges of the lines were full of fine, hair-like static, and even on the nose cone of the car—a place where the forces should have been uniform—several abrupt spikes and cliffs appeared.
The roar of the motor lasted for three minutes.
Zhang Yuan pressed the stop button.
The wind tunnel’s rotational speed slowly decreased, the roar fading into a low-frequency hum.
No one in the main control room spoke.
Zhang Yuan stared at the chaotic, sawtooth-like data on the screen and reached up to rub the back of his stiffening neck.
"The compensation term didn’t hold up."
Zhang Yuan turned and stated the obvious to Chen Zhuo.
Chen Zhuo didn’t argue.
He walked over to the monitor and leaned in to examine the staticky lines. The screen’s refresh rate was low; up close, he could see faint scan lines.
"It’s not a logical problem with the algorithm itself."
Chen Zhuo pointed to several huge, periodically occurring spikes on the screen.
"This is periodic interference. The standard, broad error compensation term is treating it as normal fluid turbulence and trying to filter it out, but it isn’t filtering it cleanly."
Zhang Yuan pulled out a chair, sat down, and casually picked up the water cup on the desk.
"This Number One small wind tunnel is one of the institute’s antiques."
Zhang Yuan took a sip of water, his tone tinged with the weary resignation of an engineer dealing with outdated equipment.
"It’s fine for rough tests, but as soon as you run a high-precision matrix algorithm like this, all its hardware flaws are laid bare."
Chen Zhuo turned to face Zhang Yuan.
"The main turbofan’s drive bearing is aging. At tens of thousands of revolutions per minute, it generates mechanical vibrations at a specific frequency, and these vibrations are transmitted through the ducts to the test model."
Zhang Yuan pointed to the spikes on the screen.
"These periodic spikes you’re seeing aren’t from wind pressure. It’s the motor vibrating."
Zhang Yuan then pointed to the data stream.
"And then there are sensors two and four. They weren’t procured from the same batch. Sensor two’s response time is about three milliseconds slower than sensor four’s. This means that in any given time slice, the data your matrix receives is misaligned. With the timing off, the solution to your equation is just a garbled mess."
Chen Zhuo listened quietly.
Conventional algorithms usually set aside a universal constant for compensation, but for a cranky old wind tunnel like this one, that kind of cure-all was clearly useless.
"Let’s eat first."
Zhang Yuan glanced at the digital clock on the wall. It was almost one.
He took two white styrofoam lunch boxes from a nearby cardboard box. They had been sitting for a while, and the containers were no longer warm.
Zhang Yuan handed a lunch box and a pair of disposable chopsticks to Chen Zhuo, then took the other for himself and expertly made his way to the hallway outside the control room.
Against the wall in the hallway was a row of old-fashioned cast-iron radiators.
Zhang Yuan squatted down right next to the radiators and opened his lunch box. Inside was braised beef with potatoes and stir-fried cabbage from the cafeteria. The food was already cold, and a thin film of grease had congealed on the surface of the potatoes.
He snapped his chopsticks apart and began shoveling down rice, completely unconcerned.
Chen Zhuo came out with his lunch box and, following Zhang Yuan’s lead, also squatted down by the radiators.
He opened his container and put a slightly tough piece of cabbage into his mouth.
Occasionally, a few other researchers in identical white lab coats would walk by. They would all nod at each other in greeting.
As he chewed his rice, Chen Zhuo stared at the fire hydrant on the opposite wall.
His mind was still replaying the sawtooth curves from the screen.
"Brother Zhang."
Chen Zhuo swallowed a mouthful of food and spoke.
"Hmm?"
Zhang Yuan mumbled a reply, his mouth full of potato.
"The factory manuals for this wind tunnel and its sensors, as well as the maintenance logs from all its major overhauls—are they all in the archive room?" Chen Zhuo asked.
Zhang Yuan stopped eating and turned to look at him.
"They’re there, yeah, locked up in the filing cabinets. What do you want that stuff for?"
"I need to know the specific tolerance data for this equipment."
Chen Zhuo poked at the rice in his lunch box with his chopsticks.
"I need precise values: the specific vibration frequency of the main bearing, the actual response delay of each sensor in milliseconds."
Zhang Yuan swallowed the food in his mouth.
"Precise values? You want to re-derive the compensation constant?"
"We can’t just apply a broad constant anymore."
Chen Zhuo said.
"I need to take this equipment’s inherent frequency bands and hardware delays and write them directly into the matrix’s low-level logic as characteristic values, creating a custom filter for it."
Zhang Yuan was stunned for a moment.
’A custom low-level filter?’
That would mean translating all the hardware parameters from mechanical engineering into constraint conditions within an algebraic matrix. The amount of work and the required level of interdisciplinary understanding were absurdly high.
"The materials in the archive room are all massive volumes," Zhang Yuan said.
"Just the mechanical drawings and parameter tables for this wind tunnel alone would be as thick as a dozen phone books stacked together, and it’s all just raw data and structural diagrams."
"Doesn’t matter."
Chen Zhuo picked up the last piece of beef, put it in his mouth, chewed twice, and swallowed. He then closed the lid on his empty lunch box.
"You go ahead and take care of your other work this afternoon. Just give me the key to the archive room."
Zhang Yuan looked at the young man squatting beside him, his expression perfectly calm.
He noticed that Chen Zhuo’s attitude in the face of this kind of experimental failure was surprisingly steady.
He didn’t complain about the crappy equipment or the dirty data; he just naturally started looking for a way to solve the practical problem at hand.
"Alright."
Zhang Yuan also finished off the rest of his food in a few quick bites, then stood up and patted down his legs.
"I’ll take you to the archive room when we’re done eating. But I’m warning you, it’s pretty dusty in there."
Zhang Yuan pulled a ring of keys from his pocket and tossed it in his hand a couple of times.
"If you get sleepy from reading, there’s a cot in the corner of the archive room."
"Thanks."
Chen Zhuo stood up and tossed his empty lunch box into a nearby trash can.
「1:30 PM.」
Chen Zhuo walked into the institute’s archive room.
Inside, rows of sheet metal cabinets stood in the shadows. Zhang Yuan helped him find all the data cards and thick binders related to the Number One wind tunnel and its sensors.
Piled on the table, the stack was a good half-meter high.
After giving a few instructions, Zhang Yuan went back to continue his maintenance work on the equipment.
Only Chen Zhuo remained in the archive room.
He pulled out a folding chair, sat down, and opened the top volume: Turbofan Drive Assembly Tolerance Chart.
The paper was slightly yellowed with age, covered in dense tables and mechanical drawings.
Chen Zhuo took out a pen and a stack of blank scratch paper.
He arranged the scratch paper, his gaze falling on the first row of data. In his mind, the cold, hard mechanical tolerances began to transform into lines of living algebraic equations.

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