Effect Of Fluid Loading Research Articles

Observation of the protagonist effect of body fluid load in the pathogenesis of sinonasal polyposis

Background: The objective is to assess the association of body fluid load in the pathogenesis of sinonasal polyposis. Subjects and Methods: The targeted cases with chronic rhinosinusitis (CRS) with nasal polyposis and control of CRS without polyposis were randomly taken from the admitted patients. Two groups of 30 people each were taken. Demographic details such as name, age, and gender were noted. Excess body water was then calculated by subtracting the perfect body water from the total body water (TBW). Results: Of 30 cases and 30 controls aged 18–60, the median was 30.5, and the mean was 34 ± 12.8 years. The gender of the case was 18 males and 12 females, while in control, the males and females were of equal number. The mean TBW was 34.4 ± 5.27 L in cases and 32.4 ± 5.87 L in controls. Total body weight was found to be higher in cases than in controls but not found to be statistically significant (P = 0.160). Excess body water was found in 60% of nasal polyps cases and 46.7% of controls, which was statistically insignificant (P = 0.301). Conclusion: There is a complex interplay between our body fluid dynamics and nasal polyp pathogenesis in CRS with polyposis. While our findings suggest potential trends with small sample sizes, further research with more extensive and diverse populations is needed to authenticate and expand on these observations.

Design of a Simple Valveless Micropump Using Piezoelectric Actuators

Abstract An open valveless micropump pumped by a disc-shaped piezoelectric actuator was developed, and its working principles were investigated. The electrode of the pump buzzer was divided into two semicircles as piezoelectric actuators, and single-phase or dual-phase AC driving potential was applied. The flow rate of the pump was analyzed when actuated in basic symmetric (W00) and anti-symmetric (W01) modes. The finite element package software ANSYS was used to analyze the resonant frequency and mode of the buzzer under fluid loading, and the vibration displacement generated by the single-phase and dual-phase time-harmonic actuation was both simulated by using an additional mass method and experimentally investigated. The experimental results show that the resonant frequency of the disc-shaped actuator decreased due to the fluid loading effect and as the gap distance between the conduit and the actuator decreased. The maximum flow rates of the W00 and W01 mode actuated pumps were 133.13 and 9.63 mL/min, respectively. The driving frequency with the highest pump efficiency was slightly lower than the resonance frequency of the fluid-loaded buzzer. Applying a hydrophobic treatment to the back of the buzzer decreased the resonance frequency under fluid loading. The results show that simulating the structural resonance frequency for various fluid loads by the additional mass method is feasible. The flow direction could be controlled by activating the W01 mode.

Tutorial on vibration and sound

Over the years I have written many tutorials on vibroacoustics. This tutorial summarizes much of the material in those articles, starting with structural flexural vibrations and how they radiate sound. I explain structural modes of vibration, how they sum into structural mobilities, and how to use infinite plate theory to estimate the means of those mobilities. I also show that as structural damping increases, the mobilities of finite structures converge to that of an infinite structure. Next, you will see how structural flexural waves radiate sound into adjacent acoustic spaces. The radiated sound power may be normalized to a nondimensional radiation efficiency. Next we will examine fluid loading effects on structures, including loading from exterior and internal acoustic regions. I will show how exterior heavy fluid loading (from water) significantly mass loads and radiation damps structural vibrations. I will also show how internal air cavities can stiffen low order structural modes, and in some cases cause coupled oscillator behavior when structural and cavity mode resonance frequencies coincide. Finally, I will explore the fundamentals of sound transmission loss through structural barriers. My complete tutorial series on vibroacoustics is available at hambricacoustics.com.

복합평판구조물의 고주파수 대역 유체/구조 연성 소음진동예측을 위한 에너지흐름유한요소해석

In this paper, the Energy Flow Finite Element Analysis (EFFEA) was performed to predict the acoustic and vibrational responses of complicated plate structures considering improved Fluid-Structure Interaction (FSI). For this, a new power transfer relationship was derived at the area junction where two different fluids are in contact on both sides of the plate. In order to increase the reliability of EFFEA of complicated plate structures immersed in a high-density fluid, the corrected flexural wavenumber and group velocity considering fluid-loading effect were derived. As the specific acoustic impedance of the fluid in contact with the plate increases, the flexural wavenumber of the plate increases. As a result, the flexural group velocity is reduced, and the spatial damping effect of the flexural energy density is increased. Additionally, for the EFFEA of arbitary-shaped built-up structures, the energy flow finite element formulation for the acoustic tetrahedral element was newly performed. Finally, for validation of the derived theory and developed software, numerical applications of complicated plate structures submerged in seawater or air were successfully performed.

Investigations on the Complex Band Diagram of Flexural Wave through the Fluid-Loaded Phononic Plate

This paper investigates the complex band diagram of flexural waves in the phononic plate with semi-infinite heavy fluid loading. The system under examination is a square plate lattice with two-dimensional periodicity immersed in a fluid domain with infinite height. The numerical models based on the wave field transformation and the Galerkin method combined with the finite element discretization technique are developed to investigate the real and imaginary parts of the dispersion relation of flexural waves propagating through the phononic plate incorporating the fluid-loading effects. A perfect agreement is found between the location and width of stop bands from the real band diagram and the attenuation diagram, which supports the validity of the numerical models. Moreover, the complex band diagram is verified by the transverse vibration transmittance of the finite phononic plate. The results demonstrate that the external fluid loading is able to adjust the location, bandwidth, and decaying level as well as affect the degree of attenuation anisotropy of the complete and directional band gaps.

Effect of Crystalloid or Colloid Fluid Loading and Vasopressor Pre-Treatment on the Timing of Hypotension in Cesarean Section with Subarachnoid Block

BACKGROUND: Cesarean section (C-section) is the most frequently performed surgery in obstetrics, generally using subarachnoid block (SAB) or epidural block for anesthesia. The previous studies have shown the effectiveness of fluid loading and vasopressor pretreatment in preventing maternal hypotension (decreased blood pressure), the most common side effect of SAB. However, the timing of hypotension in response to these treatments has not been analyzed. AIM: This study therefore aimed to compare the effects of crystalloid or colloid fluid loading and vasopressor pre-treatment on the timing of hypotension in cases of C-section under SAB anesthesia. METHODS: The study was a single-blind randomized controlled clinical trial with three treatment groups: Group I, 10 mL/kgBW crystalloid solution (Ringer’s lactate) loading 10 min before SAB; Group II, 5 mL/kgBW colloid fluid (gelatin) loading 10 min before SAB; and Group III, pretreatment with 0.1 mg/kgBW vasopressor (ephedrine) intravenous bolus just before SAB. RESULTS: Significant differences in mean blood pressure between groups were observed between the second and 8th min (p < 0.05). Hypotension was observed in the crystalloid group within the first 5 min, while average blood pressure was relatively stable all groups after the first 10 min. In addition, hypotension occurred more frequently in the crystalloid group (nine subjects, 45%), compared with the colloid and vasopressor groups (two subjects per group, 10%; p < 0.05). CONCLUSION: Hypotension occurred more rapidly and more frequently when crystalloid loading was utilized, compared with colloid loading or vasopressor pretreatment. Administration of colloid fluid loading and vasopressor pretreatment has been shown to prevent hypotension in SAB anesthesia.

Hydro-implantation versus Visco-implantation of Intraocular Lenses and Fluid Load Effect on Corneal Endothelial Cells after Uneventful Phacoemulsification

AIM: The purpose of the study was to study the effect of implantation method and fluid load (aspiration time, aspiration volume) on corneal endothelium in uneventful phacoemulsification surgeries. METHODS: This study was a prospective and interventional study involved 77 eyes, 50−81 years, divided into three groups according to implantation method (on Saline, Healon, or Methylcellulose). Specular microscope analysis of corneal endothelial parameters: Cell density (CD), central corneal thickness (CCT), coefficient of variation (CV), and Hexagonality (HEX) were done before and 3 months after surgery. RESULTS: A total of 77 eyes with cataracts were studied, and there was a significant increase in CCT and CV with a decrease in CD and HEX in all three groups. On comparing the same parameters between the three groups, there were insignificant differences regarding CCT and HEX changes. Although there was a significant change in CD, the highest loss was in the Healon group (median −0.138), followed by the Saline group (median −0.118), and the lowest was in the Methyl group (median −0.075). There was a significant change in CV, showing the highest increase in the Healon group (median 0.16129) followed by the Saline group (median 0.13307) and the lowest in the Methyl group (median 0.1266). There was a non-significant change in all corneal parameters among cases in each group with different aspiration volumes and times. CONCLUSION: Endothelial cell loss was lowest with Methyl followed by saline, and highest with Healon implantation. Fluidics had an insignificant effect in the three groups. Saline implantation was comparable to Healon, with an insignificant difference in CD loss.

Experimental Validations of Reconstructed Excitation Forces Acting Inside a Solid Enclosure. Part II: Interior Region

Part II of this paper discusses experimental validations of the reconstructed excitation forces acting inside a vibrating structure with the fluid-loading effect taken into consideration. Specifically, the characteristics of the excitation forces such as their locations, types, amplitudes, and spectra are reconstructed by using the modified Helmholtz Equation Least Squares (HELS) method, based on a single set of measurements of the normal surface velocity on the exterior surfaces, as if one could see through such a solid structure. Since the fluid-loading effect has a direct impact on the vibration responses of a structure, it is not possible to derive analytic solutions to vibration responses of the structure. Therefore, numerical solutions are sought by using the boundary element method (BEM). The fluid-loading effect, a.k.a., the reverberation sound field inside the structure is calculated based on the absorption coefficients and surface areas of the interior objects. The reconstructed excitation forces are then compared to the benchmark values and satisfactory agreements are obtained.

Experimental Validations of Reconstructed Excitation Forces Acting Inside a Solid Enclosure. Part I: Exterior Region

This paper presents the experimental validations of reconstructing the characteristics of the excitation forces that act inside a vibrating structure, which includes the location, type, amplitude, and spectrum, based on a single set of measurements of the normal surface velocity on the exterior surface by using the modified Helmholtz Equation Least Squares (HELS) method, as if one could see through this solid structure. Phase I of this paper shows the reconstruction of the vibroacoustic responses in the exterior region of the structure, including the field acoustic pressure, the surface acoustic pressure, the normal surface velocity or Operational Deflection Shape (ODS), the normal component of the time-averaged acoustic intensity, and the time-averaged acoustic power. Phase II of this paper illustrates the reconstruction of the excitation forces with the fluid-loading effects taken into consideration, based on the vibroacoustic responses reconstructed in the exterior region. The significance of the study, namely, the interrelationships among the excitation force, structural vibration, and acoustic radiation is discussed. The knowledge thus acquired may be important for engineers to analyze various complex noise and vibration issues in practice and to come up with the most cost-effective noise and vibration mitigation strategies.

Effect of Preanesthetic Fluid Loading on Postinduction Hypotension and Advanced Cardiac Parameters in Patients with Chronic Compressive Cervical Myelopathy: A Randomized Controlled Trial.

Purpose Hypotension during the early intraoperative phase is common and can lead to adverse perioperative outcomes. Fluid preloading is one of the methods to limit its occurrence. Patients with chronic compressive cervical myelopathy may have autonomic dysfunction, which can aggravate hemodynamic alterations during anesthesia. This study compared the occurrence of postinduction hypotension and changes in cardiac dynamic indices in patients with and without crystalloid preloading undergoing decompressive cervical spine surgery. Methods This randomized controlled trial was conducted over 15 months after obtaining patient consent, approval of the institute ethics committee, and trial registration. We compared preanesthetic fluid loading with Ringer's lactate (20 mL/kg over 30 minutes) with no preloading (2 mL/kg/h maintenance) in 60 consecutive patients undergoing cervical spine surgery. The ANSiscope was used to determine baseline cardiac autonomic function. Noninvasive cardiac output monitor was used to assess changes in heart rate, mean arterial pressure, cardiac index (CI), stroke volume variation (SVV), and total peripheral resistance index during study intervention, anesthetic induction, tracheal intubation, and change in position from supine to prone. Results The incidences of postinduction hypotension were 26.7% (8/30) and 86.7% (26/30) and the median doses of mephentermine used were 0 and 6 mg, respectively, in patients with and without fluid preloading (both p < 0.001). Preloading resulted in improvement in CI, reduction in SVV, and lesser vasopressor use. Conclusion Preloading reduced the occurrence of postinduction hypotension and vasopressor use, improved CI, and reduced SVV during the early intraoperative period. Registration number of Clinical Trial The trial was registered with Clinical Trial Registry of India (CTRI/2018/07/014970 on 19/07/2018).

Free vibration of FGM Mindlin plates submerged in fluid

This paper presents a free vibration analysis of functionally graded material (FGM) plates that are partially submerged in an incompressible, inviscid fluid. The FGM plates with four gradient types of continuously varying material properties along the thickness direction, including the power law, exponential, sinusoidal and cosine forms, are studied to examine various distributions of material properties. The plate is modeled based on the Mindlin Plate Theory (MPT), and the fluid loading effect on the FGM plates is modeled using the method of added mass. The variational principle is applied to derive the governing equations of this fluid-plate interaction system. The differential quadrature (DQ) method is used to solve this problem by converting the governing equations into a system of linear equations. The fundamental frequency and the corresponding mode shape are obtained using an iterative procedure. Numerical results for several examples are obtained and presented to investigate the vibration characteristics of the submerged FGM plates in terms of the gradient index, gradient type, immersed depth, fluid density, aspect ratio and slenderness ratio. Results indicate that the larger aspect ratio and immersed depth increase the fundamental frequency of the FGM plate, while larger gradient index, fluid density and slenderness ratio decrease the fundamental frequency. Among four different material gradient types, the FGM plate with power law type gradient has the smallest fundamental frequency, while the one with sinusoidal form has the largest value. The mode shape in fluid deviates from that in vacuum and shows an unsymmetrical shape for CCCC and SSSS FGM plates.

Effect of fluid load on the prognosis of children with sepsis-associated acute kidney injury undergoing continuous renal replacement therapy.

To evaluate the effect of fluid load on the prognosis of children with sepsis-associated acute kidney injury (AKI) undergoing continuous renal replacement therapy (CRRT). A total of 121 children who underwent CRRT for sepsis-associated AKI from August 2018 to March 2021 were enrolled in the retrospective study. According to the fluid load from admission or disease progression to CRRT, they were divided into three groups: low fluid load (fluid load: <5%; n=35), high fluid load (fluid load: 5% - <10%; n=35), and fluid overload (fluid load: ≥10%; n=51). Baseline data and clinical biochemical data before CRRT were collected for comparison and analysis. The Kaplan-Meier survival curve analysis was used for comparison of 28-day survival between groups. The multivariate logistic regression model was used to identify the influencing factors for the prognosis of the children. The survival analysis showed that the fluid overload group had a significantly higher 28-day mortality rate than the low fluid load and high fluid load groups (P<0.05). The multivariate logistic regression analysis showed that an increase in fluid overload volume was a risk factor for increased 28-day mortality in the fluid overload group, while earlier initiation of CRRT was a protective factor (P<0.05). Fluid overload before CRRT may increase the mortality in children with sepsis-associated AKI, and CRRT should be performed for these children as early as possible.

Determining excitation forces acting on the interior surface of an enclosure. Part I: Theory

Part I of this paper presents analytic solutions for reconstructing the excitation forces that act on the interior surfaces of a finite solid rectangular enclosure with the fluid loading effect taken into consideration, given vibroacoustic data in the exterior region. The reason for selecting a simple structure is to facilitate the reconstruction of excitation forces. To validate these analytic solutions, we apply the reciprocity principle and demonstrate that when the resultant excitation forces are used to excite the enclosure from the inside, the same vibroacoustic responses in the exterior region in exterior region can be obtained. To illustrate this point, we consider the case in which the top panel of a rectangular box is connected to the side walls through simply-supported boundary conditions, and the rest surfaces are rigid. The top surface of this box may be excited into vibrations by any type of excitation forces from the inside with the fluid loading effect taken into consideration. Note that for arbitrarily shaped structures under arbitrary boundary conditions, numerical solutions can be obtained. Therefore, it is possible to determine the excitation forces acting inside an enclosure based on the vibroacoustic information collected in the exterior. The knowledge of the excitation forces is critically important, because it can lead to optimal mitigation strategies to mitigate undesirable noise and vibrations.

An analytical study of sound transmission loss of functionally graded sandwich cylindrical nanoshell integrated with piezoelectric layers

The multidisciplinary nature of piezoelectric (PZ) structures necessitates precise and efficient methods to express their behavior under different conditions. This article extends the general usage of PZ materials by introducing acoustic and fluid loading effects in a way that an unfilled multilayer cylindrical nanoshell with a functionally graded (FG) material core and PZ layers is subjected to preliminary external electric load, acoustic waves and external flow motion. As the properties of a functionally graded material changes along the shell thickness, a power law model is assumed to be governing such variations of desired characteristics. Evidently, this system includes different types of couplings and a comprehensive approach is required to describe the structural response. To this aim, the first-order shear deformation theory (FSDT) is used to define different displacement components. Next, the coupled size-dependent vibroacoustic equations are derived based on in conjunction with nonlocal strain gradient theory (NSGT) with the aid of Hamilton’s variational principle and fluid/structure compatibility conditions. NSGT is complemented with hardening and softening material effects which can greatly enhance the precision of results. It is expected to use the findings of this paper in the optimization of similar systems by selecting suitable FG index, incident angle of sound waves, flow Mach number, nonlocal and strain gradient parameters, starting electric potential and geometric features. One of the important findings of this study is that increasing the electric voltage can obtain better sound insulation at small frequencies, specially prior to the ring frequency.

Study on vibration transfer characteristics of liquid filled double-walled cylindrical shells with elastic connection

In order to study the vibration isolation characteristics in water, based on the Flügge theory, a double-walled cylindrical shell model with spring connection is established using the wave propagation method. The fluid inside the inner shell is considered in the model. The reliability of the theoretical method is verified by comparing the calculation results of the mean square velocity with those of the finite element method. The effects of spring stiffness, spring number, fluid load, and inter-shell fluid thickness on vibration transmission of inner and outer shells are studied. The results show that the fluid loading effect of the water medium inside the inner shell can act on the inner shell and the outer shell simultaneously, while the fluid loading effect of the outboard fluid only acts on the outer shell. Under the condition of keeping the total spring stiffness unchanged, increasing the number of springs can reduce the vibration transmission from the inner shell to the outer shell, especially the vibration transmission from the inner shell to the outer shell at low frequencies. The “vibration short circuit” effect easily occurs in the inter-shell water, which is independent of the thickness of inter-shell water. When the elastic connection stiffness is small, the inter-shell water plays a leading role in vibration transmission in the whole frequency range. When the stiffness of elastic connection is large, the inter-shell water plays a leading role in vibration transmission at low frequencies, while the elastic connection plays a leading role in vibration transmission at high frequencies.

Tutorial on Acoustic Fluid Loading of Structures

Any vibrating structure is loaded by the fluid surrounding it. Whether air, water, or something else, the fluid loading adds a spatially distributed resistance (in phase with the vibration) and reactance (out of phase with the vibration) over the structural surfaces. The resistance absorbs energy, and damps structural vibrations. The reactance is either mass-like, effectively adding to the structural density, reducing resonance frequencies and vibration amplitudes; or stiffness-like, increasing resonance frequencies. Usually, mass-like reactance is caused by fluids external to a structure, and stiffness-like reactance is caused by enclosed volumes of fluids. This tutorial uses analytic methods to compare and contrast external and internal fluid loading on a flat rectangular plate and demonstrates the effects of fluid loading on plate vibration and radiated sound. The well-known stiffening effect of the internal Helmholtz resonance is demonstrated for a thin panel and a shallow entrained cavity. The differences between heavy (water) and light (air) external fluid loading are also demonstrated, with significant reductions in resonance frequencies and peak vibration amplitudes for water loading.

Drillstring Oscillations: The Influence of Fluid Loading and Stabilizer Effects

Drillstring vibrations can be undesirable for drilling operations. Here, attention is focused on vibrations of the upper portion of a drillstring as these vibrations can cause drillpipe wear and casing wear. A reduced-order model is developed to study the motions of a drillstring by taking fluid loading and stabilizer effects into account. In this model development, the distributed nature of the fluid loading is taken into account, and the drillstring is treated as a beam structure. Perturbation analyses are carried out with the reduced-order system, and the system responses are examined for primary and secondary (subharmonic and superharmonic) resonance excitations. The analytical-numerical results reveal the rich nature of the system behavior and help understand the drillstring motions during various resonance conditions.

Effects of residual stress and fluid loading on vibrations of a micro-diaphragm on a free fluid surface

In this paper, we propose a straightforward theoretical model to examine free vibrations of circular diaphragms subjected to residual stress vibrating on a free fluid surface, which is infinite in the radial direction. An incompressible and inviscid fluid is assumed, and its movement is considered to be insignificant. The mode shapes and resonant frequencies of the diaphragm are determined by the Rayleigh–Ritz approach, taking fluid–diaphragm coupling and residual stress into consideration. We also establish a finite element model to demonstrate the accuracy of the numerical calculation. The analysis shows the residual stress and fluid loading influences on the mode shapes, the natural frequencies, the non-dimensional added virtual mass incremental factors, and the mass sensitivities of the diaphragms. The proposed framework will shed new light on the fundamental understanding of numerous applications involving resonating sensors in contact with the surrounding fluid in a broad sense.

The Effect of Hypotensive Anesthesia on Hemoglobin Levels during Total Knee Arthroplasty.

Introduction: Hypotensive epidural anesthesia (HEA) is used in total joint arthroplasty as a safe and effective blood-saving modality. In order to maintain the blood pressure and heart rate patients, receive 1000 to 1500 mL of lactated Ringer’s solution during surgery. While HEA reduces the intraoperative blood loss, the effect of intravenous fluid loading on hemoglobin levels is not fully understood. The current study investigates the effect of HEA on perioperative hemoglobin levels. Materials and Methods: The study included 35 patients operated on by a single surgeon undergoing primary total knee arthroplasty under HEA. Intraoperatively, at least 300 mL of intravenous fluid were given every 15 min over the first 60 min after HEA. Blood samples were drawn before entering the operating room, after HEA, as well as after inflation of the tourniquet, every 15 min thereafter, as well as in the recovery room and on postoperative days one and two. In addition, fluid in- and outtake was recorded. Results: Patients received a mean 1275 mL during the 60 min of tourniquet time. The mean arterial pressure (MAP) 5 min after HEA dropped to 60 mmHg and reached a constant level of around 58 mmHg 15 min after HEA. The average hemoglobin level dropped from 13.9 g/dL prior to HEA, to 12.5 g/dL immediately after HEA (p < 0.001). Intraoperatively the hemoglobin level dropped further and reached 11.8 g/dL at 60 min in the absence of blood loss. Conclusions: Hypotensive epidural anesthesia and the resulting fluid substitution resulted in an average hemoglobin drop of 2.1 g/dL within the first 60 min. This needs to be taken into account when evaluating the need for blood transfusions after primary joint replacement surgery under HEA.

On the stability of rotating pipes conveying fluid in annular liquid medium

This study provides a stability analysis of flexible rotating pipes taking into account the simultaneous effects of internal and external fluid loading. Using the Euler-Bernoulli beam assumptions, governing equations for flexural vibrations of rotating pipes are obtained. The internal flow characteristics and the double gyroscopic effect are taken into account when deriving the structural equations coupled with the internal flow. External fluid loading is determined by a special linearization of the Navier-Stokes equations. Considering the circular wall of the pipe as an impermeable boundary to the flow, fluid-induced forcing functions are obtained and then applied to the structural equations of motion to get a full description of the coupled field problem. Both analytical and semi-analytical solutions are utilized to get the stability results for the coupled equations of motion. Interesting findings are reported by providing stability results for two separate categories of pipes: with purely external fluid, and simultaneous internal-flow and external-fluid loading, and some conclusions are drawn.