Study on the Behavior of Helmholtz Resonance in Different Size Bottles

The resonance is the specific response of system which is capable to vibrate with certain frequency to an external force acting with the same frequency. When air is blown across the open mouth of different bottles then air vibrate in a neck at resonant frequency. In this study we consider 5-5 bottles of different five types bottles having different of length of neck, radius of port, cross-sectional area of port and same volume (250ml). Resonance in different bottles was studied to determine how the volume of air cavity of different bottle affects the resonance. From calculated and experimental data, we found that the Helmholtz resonance frequency decreases with increase in volume and vice versa in each case of different bottles. From graph we also found that the calculated and experimental model are about 100% and 99% variability of the response data around its mean. The practical range for these different bottles is from about 256 to 512 Hz. This is about an octave plus a musical fifth near the middle of the musical instrument, so most simple musical tunes can be produced with such bottles.

Excitation of airwaves by bubble bursting in suspensions : regime transitions and implications for basaltic volcanic eruptions

Basaltic magma becomes more viscous, solid-like (elastic), and non-Newtonian (shear-thinning, non-zero yield stress) as its crystal content increases. However, the rheological effects on bubble bursting and airwave excitation are poorly understood. Here we conduct laboratory experiments to investigate these effects by injecting a bubble of volume V into a refractive index-matched suspension consisting of non-Brownian particles (volumetric fraction $$\phi$$ ϕ ) and a Newtonian liquid. We show that depending on $$\phi$$ ϕ and V, airwaves with diverse waveforms are excited, covering a frequency band of $$f = {\mathcal {O}}(10-10^4)$$ f = O ( 10 - 10 4 ) Hz. In a suspension of $$\phi \le 0.3$$ ϕ ≤ 0.3 or in a suspension of $$\phi = 0.4$$ ϕ = 0.4 with a V smaller than critical, the bubble bursts after it forms a hemispherical cap at the surface and excites a high-frequency (HF) wave ($$f \sim 1-2 \times 10^4$$ f ∼ 1 - 2 × 10 4 Hz) with an irregular waveform, which likely originates from film vibration. However, in a suspension of $$\phi = 0.4$$ ϕ = 0.4 and with a V larger than critical, the bubble bursts as soon as it protrudes above the surface, and its aperture opens slowly, exciting Helmholtz resonance with $$f = {\mathcal {O}}(10^3)$$ f = O ( 10 3 ) Hz. Superimposed on the waveform are an HF wave component excited upon bursting and a low-frequency ($$f = {\mathcal {O}}(10)$$ f = O ( 10 ) Hz) air flow vented from the deflating bubble, which becomes dominant at a large V. We interpret this transition as a result of the bubble film of a solid-like $$\phi = 0.4$$ ϕ = 0.4 suspension, being stretched faster than the critical strain rate such that it bursts by brittle failure. When the Helmholtz resonance is excited by a bursting bubble in a suspension whose surface level is further below the conduit rim, an air column (length L) resonance is triggered. For L larger than critical, the air column resonance continues longer than the Helmholtz resonance because the decay rate of the former becomes less than that of the latter. The experiments suggest that a bubble bursting at basaltic volcanoes commonly excites HF wave by film vibration. The Helmholtz resonance is likely to be excited under a limited condition, but if detected, it may be used to track the change of magma rheology or bubble V, where the V can be estimated from its frequency and decay rate.

Helmholtz Resonance Frequency of the Synthetic Jet Actuator

This paper presents the results of experimental investigations of 108 geometrical configurations of a loudspeaker-driven synthetic jet (SJ) actuator. The considered cases of the SJ actuator were characterized by a high coupling ratio. The experiment was performed to determine the impact of geometry on the Helmholtz resonance frequency. Geometrical parameters of the orifice diameter, orifice length, and cavity volume were changed within a wide range. The dependences of electrical and flow parameters that characterized the synthetic jet actuators as a function of the excitation frequency were also identified. The main goal of the research was to identify the optimal mathematical formula of the model to calculate the Helmholtz resonance frequency in the case of synthetic jet actuators. To determine the model that was characterized by the best fit of the experimental results, an additional geometrical dimensionless parameter, representing the ratio of the orifice cross-section area to the cross-section area of the cavity, was introduced. A significant impact of this parameter on the effective orifice length was noted. Based on the research findings, a model was obtained for which the results of the experiment were in the error range of ±6% for 95% of the measurement data. The obtained model is an improved version of the classical model used in the description of the resonance frequency in the case of a synthetic jet actuator. The model enables highly accurate determination of the Helmholtz resonance frequency at which the maximum synthetic jet actuator parameters occur.

Experimental and theoretical study on the internal pressure induced by the transient local failure of low-rise building roofs

A case study on the internal pressure induced by a local failure on the vulnerable gable roof of a low-rise building was extensively conducted experimentally and numerically. Five roof opening configurations were tested in the wind tunnel under three different boundary layer conditions, based on 1:40 scaled models. The effects of opening shape, opening position, opening ratio, building internal volume, and wind speed on peak transient and steady-state internal pressures were studied. The study results indicate that the peak transient and steady-state internal pressures and the corresponding transient overshoot ratio all increase with an increasing opening ratio. The peak steady-state internal pressure is little affected by the approaching wind speed; while the peak transient internal pressure coefficient shows a significant linear relationship with the wind speed. The coupling effect of vortex shedding and Helmholtz resonance in double building volume compensation situation may cause larger fluctuating internal pressure. Both the vortex shedding and Helmholtz resonance reduce the internal pressure coherence to some extent. The agreement between the numerical and experimental results is much better for the mean internal pressure than that for fluctuating internal pressure or peak internal pressure.

Beautiful Neduvangiyam also known as Nagasuram

The purpose of this study is to understand one of the earliest known non-brass double-reed instrument called Nagasuram (Nadaswaram). Our ancestors while defining Tamil music grammar in parallel focused on sound engineering, which helped them to invent new musical instruments. Sangam era alone saw more than 30 percussion and wind instruments. Among them, few instruments like Veenai, Urumi and Nagasuram are worth mentioning since their design techniques were known only to a handful of families. Their performance really stands out due to their versatile and adaptable nature to all genres of music. Music instrument, like any other scientific invention goes through the same process of trial and error before getting standardized for general use. Instruments with strong adherence to scientific and acoustic principles gain prominence among the rest, as they undergo minimal structural changes. Nagasuram (Nadaswaram) is one such instrument, which was passed on to us for generations. This instrument readily complies with acoustic principles such as sound impedance, Helmholtz resonance, wave theory etc. to get the characteristic of a loudest non-brass wind instrument.