Simultaneous Pressure Measurements Research Articles

Simultaneous measurement of ammonia concentration and gas pressure based on fiber Multi-mode and Fabry-Pérot interference

Simultaneous measurement of ammonia concentration and gas pressure based on fiber Multi-mode and Fabry-Pérot interference

Comparison of admittance and cardiac magnetic resonance generated pressure-volume loops in a porcine model

Objective. Pressure-volume loop analysis, traditionally performed by invasive pressure and volume measurements, is the optimal method for assessing ventricular function, while cardiac magnetic resonance (CMR) imaging is the gold standard for ventricular volume estimation. The aim of this study was to investigate the agreement between the assessment of end-systolic elastance (Ees) assessed with combined CMR and simultaneous pressure catheter measurements compared with admittance catheters in a porcine model. Approach. Seven healthy pigs underwent admittance-based pressure-volume loop evaluation followed by a second assessment with CMR during simultaneous pressure measurements. Main results. Admittance overestimated end-diastolic volume for both the left ventricle (LV) and the right ventricle (RV) compared with CMR. Further, there was an underestimation of RV end-systolic volume with admittance. For the RV, however, Ees was systematically higher when assessed with CMR plus simultaneous pressure measurements compared with admittance whereas there was no systematic difference in Ees but large differences between admittance and CMR-based methods for the LV. Significance. LV and RV Ees can be obtained from both admittance and CMR based techniques. There were discrepancies in volume estimates between admittance and CMR based methods, especially for the RV. RV Ees was higher when estimated by CMR with simultaneous pressure measurements compared with admittance.

Customized-accuracy simultaneous sensing of temperature, pressure and acoustic impedance based on FBS in optical fiber

In this work, it is proposed a novel customized-accuracy simultaneous sensing of temperature, pressure and acoustic impedance based on forward Brillouin scattering (FBS) in optical fiber. By observing the variations in frequency shift-temperature, frequency shift-pressure and frequency shift-acoustic impedance for different radial acoustic modes in certain types of fibers, we propose a novel method for simultaneously measuring three parameters (temperature, pressure and acoustic impedance) using the changes of frequency shift of three FBS scattering peaks. It is very interesting that we can utilize numerous sensitivity combinations of three measured parameters corresponding to different frequency shifts in optical fibers, allowing for the selection of different combinations of measurement accuracy for temperature, pressure and acoustic impedance sensing, and thus meeting the different requirements for measurement accuracy in specific measurement applications. In a proof-of-concept experiment, a 1060-XP fiber is used as the sensing fiber. By choosing suitable sensitivity combinations of coefficients of frequency shift-temperature, frequency shift-pressure and frequency shift-acoustic impedance of the fiber, we achieve high-accuracy simultaneous measurement of temperature, pressure and acoustic impedance with low measurement uncertainties of 0.13 °C, 0.04 MPa and 0.006 MRayl, respectively. The proposed method not only realize temperature, pressure and acoustic impedance simultaneous sensing for the first time, but also open up a new way of fiber optic sensing with customized multi-parameter sensing accuracy.

All-sapphire fiber-optic sensor for the simultaneous measurement of ultra-high temperature and high pressure

An all-sapphire fiber-optic extrinsic Fabry-Perot interferometric (EFPI) sensor for the simultaneous measurement of ultra-high temperature and high pressure is proposed and experimentally demonstrated. The sensor is fabricated based on all-sapphire, including a sapphire fiber, a sapphire capillary and a sapphire wafer. A femtosecond (fs) laser is employed to drill a through hole at the side wall of the sapphire capillary to allow gas flow. The sapphire fiber is inserted from one side of the sapphire capillary. The sapphire wafer is fixed at the other side of the sapphire capillary. The first Fabry-Perot (FP) cavity, composed of the end face of the sapphire fiber and the front surface of the sapphire wafer, is used for measuring pressure, while the second FP cavity, composed of the two surfaces of the sapphire wafer, is used for measuring temperature. Experimental results show that the sensor can simultaneously measure ultra-high temperature and gas pressure within the temperature range of 20 - 1400 °C and the pressure range of 0 - 5 MPa. The temperature sensitivity is 0.0033 µm/°C, and the pressure sensitivity decreases as the temperature increases, reaching 1.8016 µm/MPa and 0.3253 µm/MPa at temperatures of 20 °C and 1400 °C, respectively.

Fluid-filled versus sensor-tipped pressure guidewires for FFR and Pd/Pa measurement; PW-COMPARE study

BackgroundFluid-filled pressure guidewires are unaffected by the previously inevitable hydrostatic pressure gradient (HPG). This study aimed to compare simultaneous pressure measurements with fluid-filled and sensor-tipped pressure guidewires. MethodsFifty patients underwent fractional flow reserve (FFR) and Pd/Pa measurement with a fluid-filled and a sensor-tipped pressure guidewire simultaneously. To assess maneuverability, patients were randomized with respect to which pressure guidewire was used to cross the lesion first. Lateral fluoroscopy was used to estimate height difference between catheter tip and distal wire position (and thus HPG). Agreement between pressure measurements was studied. ResultsMeasurements were performed in LM (4% (n = 2)), LAD (44% (n = 22)), LCX (26% (n = 13)), and RCA (26% (n = 13)). Simultaneous pressure measurements showed excellent agreement (mean FFR difference − 0.01 ± 0.03 (r = 0.959, p < 0.001), mean Pd/Pa difference − 0.01 ± 0.04 (r = 0.929, p < 0.001)). FFR was ≤0.80 in 42.6% (n = 20) with fluid-filled FFR measurements versus 46.8% (n = 22) by sensor-tipped FFR measurements. Mean height difference was 15 ± 34 mm, and strongly dependent on the coronary artery (LAD 45 ± 10 mm, LCX −23 ± 16 mm, RCA −13 ± 17 mm). There was a strong correlation between height difference and difference in pressure ratios between sensor-tipped and fluid-filled pressure guidewires (FFR r = −0.850, p < 0.001; Pd/Par = −0.641, p < 0.001). Largest FFR differences were present in the LAD (−0.04 ± 0.02). After HPG correction, mean difference between HPG-corrected sensor-tipped FFR and fluid-filled FFR was 0.00 ± 0.02, mean Pd/Pa difference was 0.01 ± 0.03. ConclusionsThis study shows excellent overall correlation between FFR and Pd/Pa measurements with both pressure guidewires. Differences measured with fluid-filled and sensor-tipped pressure guidewires are vessel-specific and attributable to hydrostatic pressure gradients (NCT04802681).

Probe-Type Multi-Core Fiber Optic Sensor for Simultaneous Measurement of Seawater Salinity, Pressure, and Temperature.

In this article, we propose and demonstrate a probe-type multi-core fiber (MCF) sensor for the multi-parameter measurement of seawater. The sensor comprises an MCF and two capillary optical fibers (COFs) with distinct inner diameters, in which a 45° symmetric core reflection (SCR) structure and a step-like inner diameter capillary (SIDC) structure filled with polydimethylsiloxane (PDMS) are fabricated at the fiber end. The sensor is equipped with three channels for different measurements. The surface plasmon resonance (SPR) channel (CHSPR) based on the side-polished MCF is utilized for salinity measurement. The fiber end air cavity, forming the Fabry-Pérot interference (FPI) channel (CHFPI), is utilized for pressure and temperature measurement. Additionally, the fiber Bragg grating (FBG) channel (CHFBG), which is inscribed in the central core, serves as temperature compensation for the measurement results. By combining three sensing principles with space division multiplexing (SDM) technology, the sensor overcomes the common challenges faced by multi-parameter sensors, such as channel crosstalk and signal demodulation difficulties. The experimental results indicate that the sensor has sensitivities of 0.36 nm/‱, -10.62 nm/MPa, and -0.19 nm/°C for salinity, pressure, and temperature, respectively. As a highly integrated and easily demodulated probe-type optical fiber sensor, it can serve as a valuable reference for the development of multi-parameter fiber optic sensors.

Non-invasive pressure-volume loops using the elastance model and CMR: a porcine validation at transient pre-loads.

Pressure-volume (PV) loops have utility in the evaluation of cardiac pathophysiology but require invasive measurements. Recently, a time-varying elastance model to derive PV loops non-invasively was proposed, using left ventricular (LV) volume by cardiovascular magnetic resonance (CMR) and brachial cuff pressure as inputs. Validation was performed using CMR and pressure measurements acquired on the same day, but not simultaneously, and without varying pre-loads. This study validates the non-invasive elastance model used to estimate PV loops at varying pre-loads, compared with simultaneous measurements of invasive pressure and volume from real-time CMR, acquired concurrent to an inferior vena cava (IVC) occlusion. We performed dynamic PV loop experiments under CMR guidance in 15 pigs (n = 7 naïve, n = 8 with ischaemic cardiomyopathy). Pre-load was altered by IVC occlusion, while simultaneously acquiring invasive LV pressures and volumes from real-time CMR. Pairing pressure and volume signals yielded invasive PV loops, and model-based PV loops were derived using real-time LV volumes. Haemodynamic parameters derived from invasive and model-based PV loops were compared. Across 15 pigs, 297 PV loops were recorded. Intra-class correlation coefficient (ICC) agreement was excellent between model-based and invasive parameters: stroke work (bias = 0.007 ± 0.03 J, ICC = 0.98), potential energy (bias = 0.02 ± 0.03 J, ICC = 0.99), ventricular energy efficiency (bias = -0.7 ± 2.7%, ICC = 0.98), contractility (bias = 0.04 ± 0.1 mmHg/mL, ICC = 0.97), and ventriculoarterial coupling (bias = 0.07 ± 0.15, ICC = 0.99). All haemodynamic parameters differed between naïve and cardiomyopathy animals (P < 0.05). The invasive vs. model-based PV loop dice similarity coefficient was 0.88 ± 0.04. An elastance model-based estimation of PV loops and associated haemodynamic parameters provided accurate measurements at transient loading conditions compared with invasive PV loops.

3D hierarchical microcubic morphological composite and its application for Bi-functional Humidity/Pressure sensing in TENG architecture

Harnessing the power of contact electrification, triboelectric nanogenerators (TENGs) are a cutting-edge energy technology, where output performance is greatly influenced by the micro/nano scale architectures of triboelectric layers. We present a study on the development of TENG by introducing an advanced 3D hierarchical microcubic morphological structure prepared by simple solution casting method, employing a renewable material, lignin, in combination with eco-friendly polyvinyl alcohol (PVA) matrix. The strategic incorporation of epichlorohydrin (EPCH) as a crosslinker enhances thermal stability, and crosslinking within the lignin/PVA composite (LPC) film. A remarkable outcome of this integration is the emergence of a 3D hierarchical microcubic structure within the LPC film. This structure, with its intricate 3D arrangement, emerges as the cornerstone that underpins the development of LPC-TENGs devices distinguished by their simple fabrication process, elevated output performance, and multifaceted applications. The LPC-TENG, adorned with its unique 3D hierarchical microcubic architecture, establishes new standards in energy harvesting and sensing capabilities with a maximum output power density of 135.4 mWm−2, a short-circuit current of 6.44 μA, and a maximum output voltage of 65 V (5 times higher than PVA-based TENGs). Additionally, the LPC-TENG showed exceptional performance as a self-powered bifunctional sensing system, providing a steady output voltage range of 0–10 V across various humidity levels (20–90 % RH) and a wide usable pressure range (0–162 kPa) with a low detection limit of 1 kPa. We demonstrated the application of the LPC-TENG in energy harvesting from human walking, enabling simultaneous measurements of environmental relative humidity, pressure, and illumination of 27 commercial LEDs. The unique 3D hierarchical microcubic architecture offers an unparalleled foundation for accommodating overall performance and diverse sensing functionalities.

Reynolds-number scaling of wall-pressure–velocity correlations in wall-bounded turbulence

Wall-pressure fluctuations are a practically robust input for real-time control systems aimed at modifying wall-bounded turbulence. The scaling behaviour of the wall-pressure–velocity coupling requires investigation to properly design a controller with such input data so that it can actuate upon the desired turbulent structures. A comprehensive database from direct numerical simulations (DNS) of turbulent channel flow is used for this purpose, spanning a Reynolds-number range $Re_\tau \approx 550\unicode{x2013}5200$ . Spectral analysis reveals that the streamwise velocity is most strongly coupled to the linear term of the wall pressure, at a Reynolds-number invariant distance-from-the-wall scaling of $\lambda _x/y \approx 14$ (and $\lambda _x/y \approx 8$ for the wall-normal velocity). When extending the analysis to both homogeneous directions in $x$ and $y$ , the peak coherence is centred at $\lambda _x/\lambda _z \approx 2$ and $\lambda _x/\lambda _z \approx 1$ for $p_w$ and $u$ , and $p_w$ and $v$ , respectively. A stronger coherence is retrieved when the quadratic term of the wall pressure is concerned, but there is only little evidence for a wall-attached-eddy type of scaling. An experimental dataset comprising simultaneous measurements of wall pressure and velocity complements the DNS-based findings at one value of $Re_\tau \approx 2$ k, with ample evidence that the DNS-inferred correlations can be replicated with experimental pressure data subject to significant levels of (acoustic) facility noise. It is furthermore shown that velocity-state estimations can be achieved with good accuracy by including both the linear and quadratic terms of the wall pressure. An accuracy of up to 72 % in the binary state of the streamwise velocity fluctuations in the logarithmic region is achieved; this corresponds to a correlation coefficient of $\approx$ 0.6. This thus demonstrates that wall-pressure sensing for velocity-state estimation – e.g. for use in real-time control of wall-bounded turbulence – has merit in terms of its realization at a range of Reynolds numbers.

Pitot Tube Sensor Probe System for Simultaneous Airflow and Pressure Measurement of Expiration Inside Pulmonary Airway

Respiratory diseases, including the cronic obstructive pulmonary disease (COPD) are among the leading causes of death worldwide. To date, there is no physical examination procedure that can quantify important parameters within a specific lesion area inside the lung. In this study, we propose a novel sensor probe system consisting of a basket forceps and 2 pressure sensors to simultaneously measure the expiratory airflow and the static pressure inside the pulmonary airway. A Pitot tube mechanism using 2 pressure sensors is introduced in the system for measuring both the physical quantities. Small fiber‐optic pressure sensors with 0.3 mm diameter were utilized, and both the airflow rate and the static pressure characteristics were evaluated for obtaining the calibration curves. Finally, the proposed sensor system was implemented to measure both the airflow and pressure in an artificial ventilator and an experimental animal. The measurement of expired airflow and static pressure inside the airway of a rat with the diameter of 1.8 mm were demonstrated. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Dual transverse fiber tip Fabry-Perot cavities for simultaneous measurements of pressure and temperature

A fiber tip sensor based on dual transverse Fabry-Perot (FP) cavities for simultaneous temperature and gas pressure measurements is proposed, fabricated and tested. The proposed fiber tip sensor is formed by one-step polishing the end face of a microstructure fiber, which contains a hollow hole in the center and an eccentric core, to 45-degrees. The hybrid fiber tip sensor consists of a quartz cavity and a gas cavity effectively solving the problem of cross sensitivity in dual-parameter sensors. By tracking the shift of the interference spectra of the two FP cavities, simultaneous measurements of temperature and pressure is achieved. With advantages of a compact structure, high spatial resolution, simple fabrication and ability of multi-parameter detection, the sensor is suitable for use in a high temperature and high-pressure simultaneous sensing applications. Furthermore, the fabrication approach ensures consistent size of the FP cavities, making the sensor suitable for mass production.

Experimental investigation of instantaneous lift on NACA 0018 airfoil section due to a non-harmonic pitching motion

In this study, we explore the problem of an airfoil in a harmonic and arbitrary periodic pitching motion and seek to understand how theoretical estimation with first-order potential theory match experiments. We adopt Jones’ approximation for the Wagner function for lift computations in the time domain and Theodorsen’s model in the frequency domain. We experimentally investigate a two-dimensional symmetric NACA 0018 airfoil in pitching motion under attached flow with reduced frequencies up to 0.25 and Reynolds number varying from 1.5×105 to 3×105. To eliminate the influence of the laminar separation bubble, free-stream turbulence intensity was elevated above the baseline level by placing turbulence generating grid, thus, obtaining better compatibility between the flow conditions in the experiments and the theoretical assumptions. Time-resolved sectional lift is determined by simultaneous static pressure measurement with miniature pressure transducers. The transient response is captured with accuracy in the time domain by quantifying the non-circulatory contribution. Excellent agreement is achieved in the time and frequency domains due to the highly accurate measurement of the instantaneous magnitude and phase of the time-resolved surface pressures. We further explore the applicability of the theory for high-pitching amplitudes, which results in a temporary deviation of the measured lift from the theoretical predictions. As the frequency domain unsteady theory is more widely studied than its time domain counterpart, this study provides a unique opportunity to highlight the significance of time-domain analysis in estimating instantaneous lift in non-harmonic motion.

Accurate detection of Korotkoff sounds reveals large discrepancy between intra-arterial systolic pressure and simultaneous noninvasive measurement of blood pressure with brachial cuff sphygmomanometry.

Cardiovascular disease is the number 1 cause of death globally, with elevated blood pressure (BP) being the single largest risk factor. Hence, BP is an important physiological parameter used as an indicator of cardiovascular health. Noninvasive cuff-based automated monitoring is now the dominant method for BP measurement and irrespective of whether the oscillometric or the auscultatory method is used, all are calibrated according to the Universal Standard (ISO 81060-2:2019), which requires two trained operators to listen to Korotkoff K1 sounds for SBP and K4/K5 sounds for DBP. Hence, Korotkoff sounds are fundamental to the calibration of all NIBP devices. In this study of 40 lightly sedated patients, aged 64.1 ± 9.6 years, we compare SBP and DBP recorded directly by intra-arterial fluid filled catheters to values recorded from the onset (SBP-K) and cessation (DBP-K) of Korotkoff sounds. We demonstrate that whilst DBP-K measurements are in good agreement, with a mean difference of -0.3 ± 5.2 mmHg, SBP-K underestimates true intra-arterial SBP (IA-SBP) by an average of 14 ± 9.6 mmHg. The underestimation arises from delays in the re-opening of the brachial artery following deflation of the brachial cuff to below SBP. The reasons for this delay are not known but appear related to the difference between SBP and the pressure under the cuff as blood first begins to flow, as the cuff deflates. Linear models are presented that can correct the underestimation in SBP resulting in estimates with a mean difference of 0.2 ± 7.1 mmHg with respect to intra-arterial SBP.

Integrating Interference and Resonance Effects in Microfiber Sensors for Simultaneous Pressure and Temperature Measurement

Integrating Interference and Resonance Effects in Microfiber Sensors for Simultaneous Pressure and Temperature Measurement

Interfacial rheology of linearly growing polyelectrolyte multilayers at the water-air interface: from liquid to solid viscoelasticity.

Despite the long history of investigations of polyelectrolyte multilayer formation on solid or liquid surfaces, important questions remain open concerning the construction of the first set of layers. These are generally deposited on a first anchoring layer of different chemistry, influencing their construction and properties. We propose here an in-depth investigation of the formation of NaPSS/PAH multilayers at the air/water interface in the absence of a chemically different anchoring layer, profiting from the surface activity of NaPSS. To analyse the mechanical properties of the different layers, we combine recently established analysis techniques of an inflating/deflating bubble exploiting simultaneous shape and pressure measurement: bubble shape elastometry, general stress decomposition and capillary meniscus dynanometry. We complement these measurements by interfacial shear rheology. The obtained results allow us to confirm, first of all, the strength of the aforementioned techniques to characterize complex interfaces with non-linear viscoelastic properties. Furthermore, their sensitivity allows us to show that the multilayer properties are highly sensitive to the temporal and mechanical conditions under which they are constructed and manipulated. We nevertheless identify a robust trend showing a clear transition from a liquid-like viscoelastic membrane to a solid-like viscoelastic membrane after the deposition of 5 layers. We interpret this as the number of layers required to create a fully connected multilayer, which is consistent with previous results obtained on solid or liquid interfaces.

Fluctuating Wind Load Properties on the Surface of Inverted Umbrella-Shaped Membrane Structure Group

In the ABL wind tunnel, three inverted umbrella-shaped membrane structure groups were subjected to simultaneous pressure measurement model test. Time series of the fluctuating wind pressure were collected from 24 different wind angles. Upon examining the correlation coefficient of the fluctuating wind pressure between the upper and lower surfaces at the same pressure tap, it was discovered that the fluctuating wind pressure of the upwind roof exhibited asynchronous changes, which is a characteristic of a negative correlation area and has detrimental effects on the structure’s wind resistance. The local areas with non-Gaussian properties were evaluated by analyzing the probability density function of representative pressure taps. The mechanism behind non-Gaussian wind pressure was elucidated through considerations of the central limit theorem and spatial correlation of fluctuating wind pressure. This study introduces a quantitative classification criterion for identifying the non-Gaussian distribution area of fluctuating wind pressure, setting the threshold at an 80% cumulative probability for both skewness and kurtosis. The analysis showed that the steady airflow of the structure corresponds to the Gaussian distribution area, while the non-Gaussian distribution area is primarily concentrated at the front edge of the upwind roof and the rear edge of the downwind roof. To ascertain the peak factor for the non-Gaussian distribution, the improved peak factor method was utilized, providing insights into the range of peak factor in the non-Gaussian distribution area of this particular roof configuration. This information serves as a foundation for the wind resistance design of this structure.

Thin-core fiber-based Mach-Zehnder interferometer sensor for monitoring temperature, pressure, and humidity

A Mach-Zehnder interferometer (MZI) sensor based on thin-core fiber (TCF) is proposed. Sensitive materials such as polydimethylsiloxane (PDMS) or gelatin are coated on the surfaces of MZIs to achieve temperature, pressure, and humidity measurements. MZI is composed of single mode fiber (SMF), TCF, and multimode fiber (MMF) spliced together to form a “SMF-MMF-TCF-MMF-SMF” structure. The core/cladding diameters of TCF are 3.8 µm and 80 µm respectively. When three types of optical fibers with different core diameters are cascaded together, many cladding modes are excited to form MZI. Firstly, two similar MZI structures were fabricated designated by MZI1 and MZI2. In order to improve the sensitivity and mechanical strength, a layer of PDMS film was coated on the TCF surface of MZI1. Then, a layer of gelatin film is covered on the TCF surface of MZI2. PDMS has the high thermal expansion coefficient, thermal optical coefficient, and elasticity, and gelatin has good humidity sensitivity properties. The experimental results showed that the temperature and pressure sensitivity of MZI1 coated with PDMS reached −340 pm/°C and −14.3 nm/MPa, respectively, while the humidity sensitivity of MZI2 coated with gelatin reached −112.57 pm/% RH. When a fiber Bragg grating is cascaded with the MZI1, the sensor can achieve simultaneous measurement of temperature and pressure, eliminating crosstalk. The proposed sensor has an extremely simple structure and manufacturing method, which only involves the splicing of optical fiber and the coating by the film. In addition, the proposed sensor has a robust structure, good repeatability and stability, and high sensitivity, which has broad application prospects.

High-integration optical fiber sensor with Vernier effect based on spatial beam splitting

A highly integrated optical fiber sensor is theoretically and experimentally demonstrated, which can realize optical Vernier effect by spatial beam splitting structure. The split parallel beams could be generated by spliced non-equal-diameter hollow-core fibers (NED-HCFs). By optimizing mode-field distribution and self-imaging effect, the fringe visibility (FV) of the Vernier envelope can be enhanced to 5.11 dB. Experimental results show that the central air-waveguide has a high-pressure sensitivity of 43.42 nm/MPa, while the cladding-waveguide presents the immunity of wavelength to external pressure. The measured temperature sensitivity coefficients are −108.2 pm/℃ for Vernier envelope, 11.5 pm/℃ for cladding-waveguide. Therefore, the simultaneous measurement of pressure and temperature can be realized by using the proposed structure based on dual-parameter sensitivity matrix. Meanwhile, the sensor has a fast pressure response of 0.021 s due to the open-cavity microchannel. The proposed sensor provides a new idea for the design of optical fiber structures based on Vernier effect.

Simultaneous 24-h ambulatory blood pressure measurement on both arms: a consideration for improving hypertension management.

Arterial hypertension is one of the common treatment goals in today's medicine. 24-h ambulatory blood pressure measurement (ABPM) performed by oscillometric cuff-based devices is considered as the gold standard in hypertension diagnostics. This study aims at examining the measurement accuracy of a widely used, ABPM device. Fifty-two young and healthy participants underwent simultaneous 24-h ABPM on the left and the right upper arm using two Boso/A&D TM-2430 oscillometric cuff-based devices. Pressure curves of the cuffs, as well as hydrostatic pressure difference between the cuffs were recorded. The mean differences between both simultaneous measurements were 1.16 mmHg with limits of agreement of 36.23 mmHg for SBP and 1.32 mmHg with limits of agreement of 32.65 mmHg for DBP. Excluding measurements where the pressure curves were disturbed and correcting for hydrostatic pressure difference between the cuffs, reduced the measurement error. However, limits of agreement remained around 20 mmHg. There were large differences in hypertension grading and dipping pattern classification between simultaneous measurements on the left and right arm. The cuff-based ABPM device reveals notable measurement uncertainties, influencing hypertension grading, dipping pattern classification and blood pressure variability. These effects are attributed in part to disturbances during cuff deflation and hydrostatic influences. Nonetheless, ABPM has shown its clinical values in several studies, while this study underscores its still unlocked potential to improve hypertension management.

Columnar-jet to wall-jet state transition in transversely excited swirling flow

The current work investigates the transition of a swirling jet between two flow states, namely, columnar-jet (CJ) and wall-jet (WJ) states, under the influence of external transverse acoustic forcing. Here, we have performed simultaneous time-resolved stereoscopic particle image velocimetry and dynamic pressure measurements to understand the structure and dynamics of these swirling jets under external forcing. It is observed that at low Reynolds number (Re), the swirl flow transitions from CJ to WJ state due to transverse forcing. And the flow returns to the CJ state when the acoustic is turned OFF. However, above a critical flow Re, the swirl flow does transition from CJ to WJ state when subjected to transverse forcing, but upon turning OFF the acoustics, the flow stays in the WJ state. Thus, the swirling flow demonstrates bistability in the flow states only above a critical flow Re. It is observed that upon forcing, there is an increase in the streamwise velocity fluctuations (u′x) near the centerline and in the radial velocity fluctuations (u′r) near the injector lip. This finding is also confirmed through spectral proper orthogonal decomposition analysis. In addition, it is observed that as the flow transitions from CJ to WJ state, the relative contribution of the convective term Ur¯∂Ur¯∂r toward the radial pressure gradient (∂P¯∂r) increases in comparison to the centrifugal force term (U¯θ2r). The study highlights the effect of acoustic-induced velocity fluctuations on the bistability of swirl flows over a range of flow Re.