The Central Aerohydrodynamic Institute (TsAGI) completed the second stage of trials of a semi-model of the prospective low-noise aircraft, the institute said.

 Wind tunnel developed by TsAGI (Picture Source: TsAGI)

The aircraft is distinguished by a slightly swept wing to ensure laminar flow. The engines are mounted above the back edge of the wing. The design decreases resistance, the wing screens engine noise and bars alien objects from hitting air intakes during takeoff and landing.

"TsAGI has been dealing with laminar flow for long. The laminar profile increases technical and economic characteristics, decreases fuel consumption, resistance, etc. Aircraft with laminar flow need a simple mechanization and it can affect takeoff and landing characteristics. The slight wing sweep can decrease the speed. The surface of the laminar wing has increased requirements. Our task is to balance all pros and cons. We have to do a lot to cope with the difficult task," head of TsAGI aerodynamic department Anatoly Bolsunovsky said.

The institute has designed the concept and tested a model of a low-noise aircraft with a wing span of 2 meters. A large-scale semi-model of an aircraft with a 2.2-times bigger chord was then produced. It provides more reliable experimental results.

In 2019, the semi-model was tested in T-128 transonic wind tunnel of TsAGI. Experiments with a heat imager confirmed the presence of long laminar sections on the top surface of the wing.

The latest tests studied the boundaries of laminar flow and specified the physics of the process in takeoff and landing regimes with withdrawn Krueger flaps on the laminar wing.

TsAGI researched the flow on the aircraft surface at major angles of attack. Glued threads follow speed vector and chaotically fluctuate where the flow separates. The method exposed local separation zones which impede the high carrying capacity of the wing. The results will be used to upgrade wing mechanization and bring the effectiveness of Krueger flaps to a standard slat.

The next stage of tests is scheduled in the autumn of 2020.

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