Buzz Phenomenon Research Articles

Buzz Cycle Description in an Axisymmetric Mixed-Compression Air Intake

Buzz phenomenon is shock oscillation ahead of the supersonic air intake when its mass flow rate is decreasing at off-design condition. The buzz onset and the buzz cycle of an axisymmetric mixed-compression supersonic intake have been experimentally investigated through pressure recording and shadowgraph flow visualization. The intake was designed for a freestream Mach number of 2.0; however, tests were conducted for , 2.0, and 2.2. All tests were performed at 0 deg angle of attack. Results show that there is a strong relation between the acoustic characteristics of the intake and the buzz fluctuations. This relation causes a new pattern for the buzz oscillations, large-amplitude oscillations with large frequency, that has features of both little buzz (Ferri-type instability) and big buzz (Dailey-type instability). Flow separation caused by the shock-wave/boundary-layer interaction and acoustic compression waves are the most important driving mechanisms in the buzz cycle. Both amplitude and frequency of the buzz oscillations vary as the backpressure is varied. As the freestream Mach number is increased, the dominant frequency of the buzz oscillations is decreased.

Computational Study on Hysteretic Inlet Buzz Characteristics Under Varying Mass Flow Conditions

This paper presents a computational investigation of the hysteretic buzz characteristics of a supersonic inlet under a complete historic path of a mass flow change. It is observed that the amplitude and frequency of inlet buzz suddenly change in spite of the gradual variation in the mass flow rate. Furthermore, inlet buzz is found to exhibit quite different behavior depending on the historic path of the mass flow rate change, which leads to the hysteretic inlet buzz phenomenon. To investigate the hysteretic characteristics of inlet buzz and to provide a physical explanation of such a phenomenon, a series of numerical simulations are performed with the following three stages. First, an inlet without a center body is calculated to validate the flow solver and basic resonance mode results. Second, an inlet under a decreasing mass flow rate condition is simulated. Last, the effect of an increasing mass flow rate on inlet buzz is examined. Through computations, multiple inlet buzz transitions from fundamental to higher buzz modes are obtained, in accordance with previous experimental observations. The three sets of the computed results are compared and discussed from the viewpoint of acoustics to explain the physical mechanism of the hysteretic buzz characteristics and the buzz transition phenomenon.

축대칭 초음속 흡입구 주위의 저주파수 및 고주파수 버즈(Buzz)에 대한 수치모사

In this paper, numerical simulations of both low- and high-frequency buzz phenomena at the throttle ratios (T.R.) in Nagashima`s experiment are performed. The dominant frequencies of the low-and high-frequency buzz in the experiment are about 109 Hz with T.R.

Effects of Angle of Attack on Inlet Buzz

Anaxisymmetric supersonic inlet was tested to study the influence of angle of attack andmass flow rate on the inlet buzz phenomenon at a freestreamMach number of 2 and at various angles of attack 0–10 deg. For each angle of attack, two main frequencies for the buzz were seen in the data. For the moderate mass flow rates, small-amplitude and high-frequency oscillation occurred. In this operation stage, both highand low-frequency oscillations exist, but the higher one is dominant and is very close to the frequency of the second acoustic resonance mode. At lower mass flow, however, low-frequency and large-amplitude oscillation occurred that had a single frequency with a constant period. Increasing the angle of attack decreased the inlet performance and limited the stability margin. At intermediate values of themass flow, the buzz frequencywas seen to be independent of the angle of attack, but, for the lower mass flow rates and at high angles of attack, the frequency of the buzz at front portions of the inlet varied. However, the diffuser end still has a constant frequency. In addition, the total-pressure signal had behavior similar to that of the static data with approximately the same frequency.

Flow Characteristics of Small-Sized Supersonic Inlets

The flow characteristics were investigated for two types of small-sized supersonic inlet models: rectangular and axisymmetric inlets. The twomodels were designed by the samemethod and are of similar size, with a total length of about 160 mm. The flow phenomena that were generated at the stable and unstable operating conditions of both models are visualized and discussed in detail. The main flow feature for stable operation is the existence of a shock train induced by the shock boundary-layer interactions. The results show that the shock-train shape and position are varied along with the upstream and area ratios, which strongly impact the downstream flow and total pressure recovery. For unstable operation, various buzz phenomena are observed for different area ratios. The results indicate that the buzz phenomenon of the small-sized inlet is identical to that of a large inlet, but the small inlet can be easily affected by the presence of a separation bubble. Although the shapes of the inlets are different, the base frequencies of a big buzz for bothmodels are very similar. The role of the separation on the compression surface in the buzz process of the small-sized inlet is shown.

Supersonic inlet buzz margin control of ducted rockets

The maximum performance of a supersonic inlet will be achieved when operating as close as possible to its buzz boundary. In order to maintain high performance without crossing the buzz boundary, an active buzz margin predictor and controller is necessary. The goal of a control system is to acquire inlet buzz margin and maintain it as the designated value and predict inlet buzz before it occurs and then take some measures to buzz mitigation or inlet restart. The inlet buzz boundary and the margin of ducted rockets were first discussed and analysed. Then the dynamic mathematical model of a gas flow control system was established. Lastly, the inlet buzz margin controller of a ducted rocket was designed. Simulation results show that there exist anti-regulation characteristics for gas flow control for ducted rockets, and it leads to the particularity of inlet buzz margin control for ducted rockets in contrast to liquid ramjet. The designed inlet buzz margin has to be bigger to avoid the appearing of inlet buzz because of anti-regulation characteristics; otherwise, the inlet buzz phenomenon probably appears. If the inlet buzz of the ducted rocket appears, the command of decreasing fuel flow could not be given immediately; otherwise, the inlet buzz will aggravate.

多列円板を有する伸展式エアロスパイクの空力特性

This paper reports experimental studies on telescopic aerospikes with multiple disks. The telescopic aerospike is useful as an aerodynamic control device; however, changing its length causes a buzz phenomenon, which many researchers have reported. The occurrence of buzzing might be critical to the vehicle because it brings about severe pressure oscillations on the surface. Disks on the shaft produce stable recirculation regions by dividing the single separation flow into several conical cavity flows. The telescopic aerospikes with stabilizer disks are useful without any length constraints. Aerodynamic characteristics of the telescopic aerospikes were investigated through a series of wind tunnel tests. Transition of recirculation/reattachment flow modes of a plain spike causes a large change in the drag coefficient. Because of this hysteresis phenomenon and the buzzing, the plain spike is unsuitable for fine aerodynamic control devices. Adding stabilizer disks is effective for the improved control of aerospikes.