Pulsation Cycle Research Articles

Shock wave and bubble pulsation characteristics in a field generated by single underwater detonation

To promote the development and application of underwater detonation propulsion technology, we built a single underwater detonation experimental system and established the corresponding axisymmetric five-equation model to study the characteristics of the flow field generated by a single underwater detonation. The shock wave formed by the degeneration of the detonation wave in the detonation tube interacted with the water–gas interface. Moreover, the jetting of detonated gas was blocked by water, which sharply increased the gas pressure and yielded a transmitted wave entering the water and a reflected wave returning to the tube. The transmitted wave reached a peak pressure of 16.77 MPa at 1280 Hz. The extremely transient gas generated by detonation jetted into the water, forming bubbles with unique pulsation characteristics and completing the first pulsation cycle (28.4 ms) under the effects of the internal gas pressure and the inertia of water. In the contraction stage, the bubble changed into a complex linked annular bubble under the effects of gravity and a free surface. However, in the expansion stage, the bubble was less affected.

A new and Homogeneous metallicity scale for Galactic classical Cepheids

Context. Classical Cepheids are the most popular distance indicators and tracers of young stellar populations. The key advantage is that they are bright and they can be easily identified in Local Group and Local Volume galaxies. Their evolutionary and pulsation properties depend on their chemical abundances. Aims. The main aim of this investigation is to perform a new and accurate abundance analysis of 20 calibrating Galactic Cepheids. We used high spectral resolution (R ~ 40 000–115 000) and high S/N spectra (~400), covering the entire pulsation cycle. Methods. We focused our attention on plausible systematics that would affect the estimate of atmospheric parameters and elemental abundances along the pulsation cycle. We cleaned the line list by using atomic transition parameters based on laboratory measurements and by removing lines that are either blended or that display abundance variations along the pulsation cycle. Results. The spectroscopic approach we developed brings forward small dispersions in the variation of the atmospheric parameters (σ(Teff) ~ 50 K, σ(log g) ~ 0.2 dex, and σ(ξ) ~ 0.2 kms−1) as well as in the abundance of both iron (≲0.05 dex) and α elements (≲0.10 dex) over the entire pulsation cycle. We also provide new and accurate effective temperature templates by splitting the calibrating Cepheids into four different period bins, ranging from short to long periods. For each period bin, we performed an analytical fit with Fourier series providing θ = 5040/Teff as a function of the pulsation phase. Conclusions. The current findings are a good viaticum for tracing the chemical enrichment of the Galactic thin disk by using classical Cepheids as a fundamental stepping stone for further investigations into the more metal-poor regime that is typical of Magellanic Cepheids.

Numerical analysis of heat transfer improvement for pulsating flow in a periodic corrugated channel with discrete V-type winglets

In the present study, the effects on the hydraulic and thermal performance of pulsating flow in a periodic corrugated channel with discrete V-type winglets were numerically investigated. Three different channel flows were considered with non-winglet, solid winglet, and perforated winglet configurations. The winglets were placed in the center of the channel in a discrete V-shape downstream. Numerical analyses were carried out with the finite volume approach. The effects of pulsation amplitude (A), Strouhal number (St), and Reynolds number (Re) on the flow and heat transfer were examined. The upper and lower surfaces of the corrugated channel were protected at Tw = 350 K and thermal performance and pressure drop were acquired for a pulsating cycle across the channel. The numerical results were presented in terms of thermal performance (η), dimensionless friction factor (Γ), and thermal performance factor (TPF). To observe the effects of the pulsation parameters and Reynolds number, time-averaged velocity and temperature distributions in the channels were obtained. The findings showed that the flow and heat transfer characteristics were highly affected by the channel and winglet geometry. The pulsation parameters significantly contributed to heat transfer improvement, especially at high Reynolds numbers. Thermal performance increased considerably with increasing pulsation amplitude and frequency with a slight increase in friction factor. Also, it was observed that the perforated winglets reduced the friction factor compared to the solid winglets. The highest TPF values for non-winglet, solid winglet, and perforated winglet configurations were respectively found as 5.71, 4.68, and 5.17 at Re = 1000, A = 1.5, and St = 8.

Pulsating propagation and extinction of hydrogen detonations in ultrafine water sprays

Pulsating detonation and extinction in stoichiometric hydrogen/oxygen/argon gas with water sprays are studied for the first time. Eulerian-Lagrangian method is employed, and the emphasis is laid on characterization of the unsteady phenomena and evolutions of chemical / flow structures in pulsating propagation and extinction. Three detonation propagation modes are found: (1) pulsating propagation, (2) propagation followed by extinction, and (3) immediate extinction. For pulsating detonation, within one cycle, the propagation speeds and the distance between reaction front (RF) and shock front (SF) change periodically. The pulsating phenomenon originates from the interactions between gas dynamics, chemical kinetics, and droplet dynamics inside the induction zone. Multiple pressure waves are emanated from the RF within one cycle, which overtake and intensify the lead SF. An autoigniting spot arises in the shocked gas after the contact surface. The relative locations of SF, RF, shock-frame sonic point, and two-phase contact surface remain unchanged in a pulsating cycle, but their distances have periodic variations. Moreover, detonation extinction is featured by continuously increased distance between the RF and SF and quickly reduced pressure peaks, temperature, and combustion heat release. The decoupling of RF and SF leads to significantly increasing chemical timescale of the shocked mixture. The hydrodynamic structure also changes considerably when detonation extinction occurs. Moreover, the predicted map of detonation propagation and extinction illustrates that the critical mass loading for detonation extinction reduces significantly when the droplet size becomes smaller. It is also found that for the same droplet size, the average detonation speed monotonically decreases with water mass loading. However, detonation speed and pulsating frequency have a non-monotonic dependence on droplet size under a constant water mass loading.

Experimental study of vortex formation in pulsating jet flow by time-resolved particle image velocimetry

We experimentally investigate the pulsating circular jet flow at moderate Reynolds numbers. By applying time-resolved particle image velocimetry in the axial-radial plane, we measure the near-field velocity fields with the jet source temporally modulated by sinusoidal pulsations. As a baseline, the steady jet flow with the same mean Reynolds number is tested. The direct comparisons of the mean and fluctuating velocity fields show that the whole potential core as well as the axisymmetric shear layer is modulated by the pulsation effect. Meanwhile, larger-scale vortices are formed in the shear layer with phase correlation of the pulsation cycle. As a result, the pulsation increases the turbulent mixing in the latter half of the potential core, and it extends the fluid entrainment further in the radial direction. The increased fluid entrainment of the ambient quiescent fluid is clearly identified by the attracting Lagrangian coherent structures as the bounds of the growing vortices within the shear layer. By analyzing the dynamic modes, we find that the low-frequency off-the-axis helical structures, which are dominant in the steady jet flow, are inhibited. The axisymmetric jet column mode and its harmonics along the axis are strengthened by the pulsation effect. Furthermore, the vortex formation mainly takes place particularly in the deceleration phase, whereas a shock-like wave front is formed during the acceleration, indicating the distinct roles of the pulsation phases in the jet instability.

Establishing the influence of technical and technological parameters of milking equipment on the efficiency of machine milking

One of the tasks that imply increasing the milk productivity of cows is to create optimal maintenance conditions that ensure the increased use of the genetic potential of cattle based on the implementation of engineering and technological solutions. A mathematical model has been built that links the technical and technological parameters of the vacuum system of milking equipment, namely, the value of the working vacuum P, the pulsation frequency n, the ratio of pulsation cycles, and the tension strength of milking rubber FH to cows’ milk yield rate V. The range of milking plant operating parameters for milking in the milk line has been determined, at which the milk yield rate is maximum: P=52 kPa, n=57.6–58.8 min–1, δ=0.59–0.64, FH=59.3–60.4 H. Under these parameters, the milk yield rate is V=1.48–1.53 l/min. The results of the multifactor experiment have helped construct an adequate mathematical model of the second order, which confirms the theoretical dependence of the influence of the technical and technological parameters of the vacuum system of milking equipment on milk yield rate and the air flow of the milking machine. Analysis of the mathematical model has made it possible to establish the rational structural and technological parameters for the vacuum system of a milking machine: the value of the working vacuum, P=50.6 kPa; pulsation frequency, n=55.9 min–1, the ratio of pulsation cycles and the tension force of milking rubber FH=64.8 H. Under these parameters, the milk yield rate is maximum: V=1.47–1.52 l/min; the air flow consumption of the milking machine is Q=2.19 m3/h. The mathematical model built fully reveals the influence of technical and technological parameters of milking equipment on the efficiency of machine milking. Owing to this, the issue related to the rational choice of equipment is resolved.

Potential Association Between the Low-Energy Plasma Structure and the Patchy Pulsating Aurora

While the pulsating auroral phenomena have been recognized and studied for decades, our understating of their generation mechanisms remains incomplete to date. In one main class of pulsating auroras which is termed “patchy pulsating auroras” (PPA), the auroral patches are found to basically maintain their shape and size over many pulsation cycles. Also, PPAs are repeatedly found to essentially co-move with the ExB convection drift. The above properties led many researchers to hypothesize that PPA might connect to a structure of enhanced cold plasma in the magnetosphere. In this study, we review the existing evidence, and provide new perspective and support, of the low-energy plasma structure potentially associated with PPA. Based on observations from both the magnetosphere and the topside ionosphere, we suggest that ionospheric auroral outflows might constitute one possible source mechanism of the flux tubes with enhanced low-energy plasma that connect to the PPA. We also review the existing theories of pulsating auroras, with particular focus on the role of low-energy plasma in these theories. To date, none of the existing theories are complete and mature enough to offer a quantitatively satisfactory explanation of pulsating auroras. At last, we suggest a few future research directions to advance our understanding of pulsating auroras: a) more accurate measurements of the cold plasma density, b) more developed theories of the underlying mechanisms of ELF/VLF wave modulation, and c) auxiliary processes in the topside ionosphere or near-Earth region accompanying pulsating auroras.

Magnetic field of pulsating stars

To date, magnetic fields have been detected in various types of pulsating stars. For several of these stars, the variability of the magnetic field with their radial pulsation period was confirmed. The physical mechanism of the pulsation variability of the magnetic field remains unknown. We discuss the current state of the problem of magnetic field variability over pulsation cycles in radially pulsating stars.

Data-based estimation and simulation of compressible pulsating flow with reverse-flow through an orifice

Highly compressible pulsating flows are often encountered in devices where knowledge of the flow rate is required but elimination of pulsations is not an option. The current work is a continuation of a previous investigation that characterized the orifice discharge coefficient Cd as a function of dimensionless groups based on pulsation characteristics. The experimental apparatus has been rebuilt in the current work to mitigate temperature and vibration problems, allowing pressure and ΔP measurements to be made very close to the test section with 159-mm of nylon tubing. Data was acquired for 77 operating conditions spanning a range of pulsation frequencies, mass flow rates and system pressures. They confirm previously reported low Cd's in 0.20 range (calculated from time-averaged pressures) at some high-pressure low-flow operating conditions. Computational Fluid Dynamics (CFD) simulations of 12 of these data points suggest that the low Cd's result from reverse flow. Flow direction changed several times during each pulsation cycle closely tracking the orifice ΔP. A ‘core-and-sheath’ phenomena was observed for reverse-flow operating conditions: a positive core flow surrounded by a sheath of negative flow transitioned to a negative core and positive sheath several times during each pulsation cycle. The simulations also suggested that velocity profiles at the orifice stay stable and similar to steady-state profiles except for periods of rapid transitions. Based on these results a data-based quasi-steady method of estimating pulsating flow has been proposed. A pair of forward and reverse flow Cd's chosen by the data are used to predict instantaneous forward and reverse flows using the steady-state orifice discharge equation for compressible flow. The instantaneous values are then summed up over the pulsation cycle to estimate average mass flow rate. Average prediction errors were within 6%. A previously proposed method where regression was used to model Cd as a function of dimensionless groupings was shown to produce similar results. Both methods are designed to extract information from experimental data in order to overcome theoretical limitations and experimental error. The data is available upon request for further understanding of the flow physics.

Investigation of pulsatile flow structure in closed-type cavity

Pulsatile flow in a channel with sudden expansion and contraction, referred to as a closed-type cavity, is experimentally and numerically investigated in the range of Re = 50–1650, covering laminar and transitional flow regimes. Investigations are performed in the range of pulsation frequencies corresponding to Wo = 0.28–0.62 and at a constant pulsation amplitude. Pulsation frequency influence to time-averaged recirculation zone length and the development of recirculation zone as well as upper and corner eddies during the pulse cycle at different pulsation frequencies are investigated. A fixed amplitude from zero to maximum velocity is chosen to investigate flow behaviour throughout a whole pulsation cycle. The results show that the pulsation effect on the recirculation zone length is insignificant in the laminar flow regime at investigated frequencies. However, in the transitional flow regime, recirculation zone length was shortened, regardless of the Wo. The analysis of recirculation zone and upper eddy dynamics during the pulse cycle revealed that their growth rate depends on Wo. The development lag effect is observed at certain velocity phase angles. The analysis of shear rate and turbulence intensity profiles revealed that increased instabilities are determined by the interaction of recirculation zone, upper eddy and the forward-facing step during the pulse cycle.

Transient linear stability of pulsating Poiseuille flow using optimally time-dependent modes

Time-dependent flows are notoriously challenging for classical linear stability analysis. Most progress in understanding the linear stability of these flows has been made for time-periodic flows via Floquet theory focusing on time-asymptotic stability. However, little attention has been given to the transient intracyclic linear stability of periodic flows since no general tools exist for its analysis. In this work, we explore the potential of using the recent framework of the optimally time-dependent (OTD) modes (Babaee & Sapsis, Proc. R. Soc. Lond. A, vol. 472, 2016, 20150779) to extract information about both the transient and the time-asymptotic linear stability of pulsating Poiseuille flow. The analysis of the instantaneous OTD modes in the limit cycle leads to the identification of the dominant instability mechanism of pulsating Poiseuille flow by comparing them with the spectrum and the eigenmodes of the Orr–Sommerfeld operator. In accordance with evidence from recent direct numerical simulations, it is found that structures akin to Tollmien–Schlichting waves are the dominant feature over a large range of pulsation amplitudes and frequencies but that for low pulsation frequencies these modes disappear during the damping phase of the pulsation cycle as the pulsation amplitude is increased beyond a threshold value. The maximum achievable non-normal growth rate during the limit cycle was found to be nearly identical to that in plane Poiseuille flow. The existence of subharmonic perturbation cycles compared with the base flow pulsation is documented for the first time in pulsating Poiseuille flow.

Optimal energy growth in pulsatile channel and pipe flows

Pulsatile channel and pipe flows constitute a fundamental flow configuration with significant bearing on many applications in the engineering and medical sciences. Rotating machinery, hydraulic pumps or cardiovascular systems are dominated by time-periodic flows, and their stability characteristics play an important role in their efficient and proper operation. While previous work has mainly concentrated on the modal, harmonic response to an oscillatory or pulsatile base flow, this study employs a direct–adjoint optimisation technique to assess short-term instabilities, identify transient energy-amplification mechanisms and determine their prevalence within a wide parameter space. At low pulsation amplitudes, the transient dynamics is found to be similar to that resulting from the equivalent steady parabolic flow profile, and the oscillating flow component appears to have only a weak effect. After a critical pulsation amplitude is surpassed, linear transient growth is shown to increase exponentially with the pulsation amplitude and to occur mainly during the slow part of the pulsation cycle. In this latter regime, a detailed analysis of the energy transfer mechanisms demonstrates that the huge linear transient growth factors are the result of an optimal combination of Orr mechanism and intracyclic normal-mode growth during half a pulsation cycle. Two-dimensional sinuous perturbations are favoured in channel flow, while pipe flow is dominated by helical perturbations. An extensive parameter study is presented that tracks these flow features across variations in the pulsation amplitude, Reynolds and Womersley numbers, perturbation wavenumbers and imposed time horizon.

A Radial-velocity Search for Binary RR Lyrae Variables

Abstract We report 272 radial velocities for 19 RR Lyrae variables. For most of the stars we have radial velocities for the complete pulsation cycle. These data are used to determine robust center-of-mass radial velocities that have been compared to values from the literature in a search for evidence of binary systems. Center-of-mass velocities were determined for each star using Fourier Series and template fits to the radial velocities. Our center-of-mass velocities have uncertainties from ±0.16 km s−1 to ±2.5 km s−1, with a mean uncertainty of ±0.92 km s−1. We combined our center-of-mass velocities with values from the literature to look for deviations from the mean center-of-mass velocity of each star. Fifteen RR Lyrae show no evidence of binary motion (BK And, CI And, Z CVn, DM Cyg, BK Dra, RR Gem, XX Hya, SZ Leo, BX Leo, TT Lyn, CN Lyr, TU Per, U Tri, RV UMa, and AV Vir). In most cases this conclusion is reached due to the sporadic sampling of the center-of-mass velocities over time. Three RR Lyrae show suspicious variation in the center-of-mass velocities that may indicate binary motion but do not prove it (SS Leo, ST Leo, and AO Peg). TU UMa was observed by us near a predicted periastron passage (at 0.14 in orbital phase) but the absence of additional center-of-mass velocities near periastron makes the binary detection, based on radial velocities alone, uncertain. Two stars in our sample show Hγ emission in phases 0.9–1.0: SS Leo and TU UMa.

X-Rays in Cepheids: XMM-Newton Observations of η Aql*

Abstract X-ray bursts have recently been discovered in the Cepheids δ Cep and β Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid η Aql with the XMM-Newton satellite at the phase of maximum radius; the phase at which there is a burst of X-rays in δ Cep. No X-rays were seen from the Cepheid η Aql at this phase, and the implications for Cepheid upper atmospheres are discussed. We have also used the combination of X-ray sources, as well as Gaia and 2MASS data, to search for a possible grouping around the young intermediate mass Cepheid. No indication of such a group was found.

Atmosphere of Betelgeuse before and during the Great Dimming event revealed by tomography

Context. Despite being the best studied red supergiant star in our Galaxy, the physics behind the photometric variability and mass loss of Betelgeuse is poorly understood. Moreover, recently the star has experienced an unusual fading with its visual magnitude reaching a historical minimum. The nature of this event was investigated by several studies where mechanisms, such as episodic mass loss and the presence of dark spots in the photosphere, were invoked. Aims. We aim to relate the atmospheric dynamics of Betelgeuse to its photometric variability, with the main focus on the dimming event. Methods. We used the tomographic method which allowed us to probe different depths in the stellar atmosphere and to recover the corresponding disk-averaged velocity field. The method was applied to a series of high-resolution HERMES observations of Betelgeuse. Variations in the velocity field were then compared with photometric and spectroscopic variations. Results. The tomographic method reveals that the succession of two shocks along our line-of-sight (in February 2018 and January 2019), the second one amplifying the effect of the first one, combined with underlying convection and/or outward motion present at this phase of the 400 d pulsation cycle, produced a rapid expansion of a portion of the atmosphere of Betelgeuse and an outflow between October 2019 and February 2020. This resulted in a sudden increase in molecular opacity in the cooler upper atmosphere of Betelgeuse and, thus, in the observed unusual decrease of the star’s brightness.

Numerical study on the flow and heat transfer of water-based Al2O3 forced pulsating nanofluids based on self-excited oscillation chamber structure

In this study, the flow and heat transfer characteristics of the forced pulsating Al2O3-water nanofluid were numerically studied. The pulsating excitation of the nanofluid is provided by the Helmhertz self-excited oscillating cavity. The large eddy simulation method is used to solve the equation, and the local Nusselt number and heat transfer performance index are used to analyze the heat transfer characteristics of the nanofluid in the self-excited oscillation heat exchange tube. In addition, the effect of different downstream tube diameters on heat transfer enhancement is discussed. The research results show that the existence of the countercurrent vortex can increase the disturbance of the near-wall fluid, thereby improving the mixing degree of the near-wall fluid and the central mainstream. As the countercurrent vortex migrates downstream, pulse enhanced heat transfer is realized. Furthermore, it was also found that when the downstream tube diameter d2 = 1.8d1, the periodic effect of the local Nusselt number of the wall is the best and the heat transfer performance index has the most stable pulsation effect within a pulsation cycle. But when d2 = 2.0d1, the change curve of heat transfer performance index in a pulsating period is the highest, the maximum value is 3.95.

Analytical model for electromagnetic induction in pulsating ferrofluid pipe flows

Energy harvesting processes using ferrofluidic induction—a process that generates voltage via the pulsation of a ferrofluid (iron-based nanofluid) through a solenoid—have received increasing attention over the past decade. In this paper an analytical model is proposed to predict the induced electromotive force (EMF) based on the flow behavior and magnetic properties of a pulsating ferrofluid energy harvesting device. The ferrofluid is treated as an idealized series of discrete magnetic ‘slugs’ within passing through the solenoid, and the model identifies key parameters for describing and optimizing ferrofluidic induction in pulsating pipe flows. The resulting expression for induced EMF as a function of slug position relative to the solenoid is numerically integrated to determine the root mean square (RMS) of EMF during one pulsation cycle. Data from a previously documented study using an experimental induced EMF test rig is analyzed to find corresponding measured values of EMF RMS and used to validate the analytical model. Experimental and analytical results both show an increase in induced EMF with higher pulse frequency, increased number of bias magnets, and reduced spacing between the magnet and solenoid. At low magnetic flux densities and pumping frequencies, the EMF is negligible; with 0.3 mT magnetic flux density and 9 and 18 Hz pumping frequencies the measured RMS is nominally zero. For a 9 Hz pumping frequency the RMS value of the induced EMF is less than 1 μV at all magnetic flux densities. For the highest pumping frequency examined, 30 Hz, the induced EMF RMS is greater than 1 μV for all magnetic flux densities greater than 0.7 mT. As the experimentally measured values of EMF lie within the uncertainty bounds of the model, induced EMF can be predicted within an order of magnitude for magnetic fluid-induced energy harvesting systems.

Effect of Sinusoidally Varying Flow of Yield Stress Fluid on Heat Transfer From a Cylinder

Abstract The effect of pulsating laminar flow of a Bingham plastic fluid on heat transfer from a constant temperature cylinder is studied numerically over wide ranges of conditions as Reynolds number (0.1 ≤ Re ≤ 40) and Bingham number (0.01 ≤ Bn ≤ 50) based on the mean velocity, Prandtl number (10 ≤ Pr ≤ 100), pulsation frequency (0 ≤ ω* ≤ π), and amplitude (0 ≤ A ≤ 0.8). Results are visualized in terms of instantaneous streamlines, isotherms, and apparent yield surfaces at different instants of time during a pulsation cycle. The overall behavior is discussed in terms of the instantaneous and time-averaged values of the drag coefficient and Nusselt number. The size of the yielded zone is nearly in phase with the pulsating velocity, whereas the phase shift has been observed in both drag coefficient and Nusselt number. The maximum augmentation (∼30%) in Nusselt number occurs at Bn = 1, Re = 40, Pr = 100, ω* = π, and A = 0.8 with respect to that for uniform flow. However, the increasing yield stress tends to suppress the potential for heat transfer enhancement. Conversely, this technique of process intensification is best suited for Newtonian fluids in the limit of Bn → 0. Finally, a simple expression consolidates the numerical values of the time-averaged Nusselt number as a function of the pertinent dimensionless parameters, which is consistent with the widely accepted scaling of the Nusselt number with ∼Pe1/3 under these conditions.

SiO, 29SiO, and 30SiO emission from 67 oxygen-rich stars. A survey of 61 maser lines from 7 to 1 mm.

Circumstellar environments of oxygen-rich stars are among the strongest SiO maser emitters. Physical processes such as collisions, infrared pumping and overlaps favors the inversion of level population and produce maser emission at different vibrational states. Despite numerous observational and theoretical efforts, we still do not have an unified picture including all the physical processes involved in the SiO maser emission. The aim of this work is to provide homogeneous data in a large sample of oxygen-rich stars. We present a survey of 67 oxygen-rich stars from 7 to 1 mm, in their rotational transitions from J = 1 → 0 to J = 5 → 4, for vibrational numbers v from 0 to 6 in the three main SiO isotopologues. We have used one of the 34 m NASA antennas at Robledo and the IRAM 30 m radio telescope. The first tentative detection of a v = 6 line is reported, as well as the detection of new maser lines. The highest vibrational levels seem confined to small volumes, presumably close to the stars. The J = 1 → 0, v = 2 line flux is greater than the corresponding v = 1 in almost half of the sample, which may confirm a predicted dependence on the pulsation cycle. This database is potentially useful in models which should consider most of the physical agents, time dependency, and mass-loss rates. As by-product, we report detections of 27 thermal rotational lines from other molecules, including isotopologues of SiS, H2S, SO, SO2, and NaCl.

Spectroscopic and Photometric Monitoring of a Poorly Known Highly Luminous OH/IR Star: IRAS 18278+0931

Abstract We present the time-dependent properties of a poorly known OH/IR star, IRAS 18278+0931 (hereafter IRAS 18+09), toward the Ophiuchus constellation. We have carried out long-term optical/near-infrared photometric and spectroscopic observations to study the object. From optical R- and I-band light curves, the period of IRAS 18+09 is estimated to be 575 ± 30 days and the variability amplitudes range from ΔR ∼ 4.0 mag to ΔI ∼ 3.5 mag. From the standard period–luminosity relations, the distance (D) to the object, 4.0 ± 1.3 kpc, is estimated. Applying this distance in the radiative transfer model, the spectral energy distribution is constructed from multiwavelength photometric and IRAS-LRS spectral data, which provide the luminosity, optical depth, and gas mass-loss rate of the object to be 9600 ± 500 L ⊙, 9.1 ± 0.6 at 0.55 μm, and 1.0 × 10−6 M ⊙ yr−1, respectively. The current mass of the object is inferred to be in the range 1.0−1.5 M ⊙ assuming solar metallicity. Notably, the temporal variation of atomic and molecular features (e.g., TiO, Na i, Ca i, CO, H2O) over the pulsation cycle of the OH/IR star illustrates the sensitivity of the spectral features to the dynamical atmosphere as observed in pulsating AGB stars.