# Naca Scoop Element

## Naca Scoop Element General Description

A NACA duct also sometimes called a NACA scoop or NACA inlet, is a common form of low-drag air inlet design. A NACA duct allows air to flow into an internal duct, often for cooling purposes, with a minimal disturbance to the flow. The design was originally called a submerged inlet, since it consists of a shallow ramp with curved walls recessed into the exposed surface of a streamlined body. Flow Simulator Naca scoop element calculate pressure recovery factor & flow rates through scoop/flush type inlets for given geometry & operating conditions.

## Quick Guide for Naca Scoop Element Creation in the GUI

There are three subtypes of Naca Scoop elements available in Flow Simulator. This element is available only for Compressible (e.g. gas systems) analysis. The various subtypes are

1. Scoop inlets
2. Flush Inlets (NACA based Formulations)
3. Flush Inlets (ESDU based formulations)

Typical Geometry inputs that are required to model Naca Inlets are provided in the below images

Flush Type:

Scoop type:

## Naca Scoop Element Inputs

Table of the inputs for the Naca Scoop Element.

## Naca Scoop Element Theory Manual

 Nomenclature: W: Mass flow rate Specific heat Ratio Tt: Total Temperature R: Gas Constant Pt: Total pressure Density Ps: Static pressure Cp: Specific Heat MN: Mach Number gc: Gravitational Constant V: Velocity Subscripts: up: Upstream station dn: Downstream station

Scoop Type Inlets

Flush Type Inlets (Naca Method)

Flush Type Inlets (ESDU Method)

For Additional Momentum loss, Portion of Upstream Dynamic Head loss, Exit K Loss refer Solver General theory section.

## Naca Scoop Element Outputs

The following table listing contains output variables common to all Inlet scoop types.

Name Description Units
UPSTREAM: PT Upstream (station 0) driving pressure (like PTS of other element types). psi, mPa
UPSTREAM: PS Upstream (station 0) static pressure. psi, mPa
UPSTREAM: TT Upstream (station 0) total temperature. deg F, K
UPSTREAM: TS Upstream (station 0) static temperature. deg F, K
UPSTREAM: MN Upstream (station 0) Mach number. (unitless)
UPSTREAM: VEL Upstream (station 0) velocity. ft/s, m/s
UPSTREAM: AOA Angle of attack of incoming air (station 0). deg
THROAT: PT Throat (station 1) driving pressure (like PTS of other element types). psi, mPa
THROAT: PS Throat (station 1) static pressure. psi, mPa
THROAT: TT Throat (station 1) total temperature. deg F, K
THROAT: TS Throat (station 1) static temperature. deg F, K
THROAT: MN Throat (station 1) Mach number. (unitless)
THROAT: VEL Throat (station 1) velocity. ft/s, m/s
THROAT: VRAT Velocity ratio (Vstation1 / Vstation). (unitless)
IDEAL_MDOT Ideal mass flow rate. lbm/sec
CD Actual mass flow rate divided by ideal mass flow rate. (unitless)
INLET_HEIGHT

Inlet throat height.

(Echo of the user input value.)

in, m
INLET_WIDTH

Inlet throat width.

(Echo of the user input value.)

in, m
INLET_AREA Inlet throat area (height * width). inch2, m2
INLET_ASPECT_RATIO Inlet throat aspect ratio (width / height). (unitless)

The following table listing contains output variables unique to the NACA Inlet Scoop (SUBTYPE=0).

 Name Description Units NACELLE_DIST Distance from leading edge of the nacelle to the start of the Inlet. (Echo of the user input value.) in, m REY Reynolds Number based on distance from the nacelle leading edge. (unitless) BND_LAY_THK Turbulent flat plate boundary layer thickness. in, m P_RATIO Pressure ratio (PT1 / PT0), (PTinlet / PTfreestream) (unitless)

The following table listing contains output variables unique to the NACA Flush Scoop (SUBTYPE=1).

 Name Description Units RAM_P_EFF Ram Pressure Efficiency (recovery factor) after adjustments (PT1-PS0)/(PT0-PS0). (unitless)

The following table listing contains output variables unique to the ESDU Flush Scoop (SUBTYPE=2).

 Name Description Units INLET_LIP_HEIGHT Flush lip height. (Echo of the user input value.) in, m NACELLE_DIST Distance from leading edge of the nacelle to the start of the Inlet. (Echo of the user input value.) in, m REY Reynolds Number based on distance from the nacelle leading edge. (unitless) BND_LAY_THK Turbulent flat plate boundary layer thickness. in, m MOM_LAY_THK Turbulent flat plate momentum layer thickness. in, m RAMP_ANGLE Ramp angle. (Echo of the user input value.) deg RAM_P_EFF Ram Pressure Efficiency after adjustments (PT1-PS0)/(PT0-PS0), ETTA in ESDU paper. (unitless) BASE_EFF Ram Pressure Efficiency before adjustments (PT1-PS0)/(PT0-PS0). (unitless) MFLO_COR Delta Ram Pressure Efficiency due to the mass flow not equal to full mass flow. (unitless) RAMP_ANG_COR Delta Ram Pressure Efficiency due to the ramp angle. (unitless) ASRAT_COR Delta Ram Pressure Efficiency due to the aspect ratio. (unitless)

## References

1. ESDU Report 86002, The Royal Aeronautical Society, “Drag and pressure recovery characteristics of auxilary air inlets at subsonic speeds, 2004
2. NACA Report 5120, Charles W Frick, Wallace F Davis, Laurce M. Randall, and Emmet A Mossman, “An experimental investigation of NACA submerged duct entrances, 1951
3. NACA Report R-72156, Laurce M. Randall, and Emmet A Mossman “An experimental investigation of the design variables for NACA submerged duct entrances, 1948
4. NACA Report A8F21, Norman J., Martin, Curt A. Holshauser, “An experimental investigation at large scale of several configurations of an NACA submerged air intake, 1954
5. NACA Report A8I29, Charles F. Hall, Joseph L. Frank, “Ram recovery characteristics of NACA submerged inlets at high subsonic speeds, 1948
6. NACA Report RML50H15, P. Kenneth Perpont, Robert R. Howell, “Low speed investigation of a submerged air scoop with and without boundary layer suction, 1951
7. NACA Report L57B07, John S Dennard, “A transonic investigation of the mass flow and pressure recovery characteristics of several types of auxillary air inlets, 1957
8. NACA Report 2323, Alvin H Sacks, John R Spreiter, “Theoretical investigation of submerged inlets at low speeds, 1951